A child with a congenital solitary functioning kidney (SFK) may develop kidney disease from early in life due to hyperfiltration injury. Previously, we showed in a sheep model of SFK that brief angiotensin-converting enzyme inhibition (ACEi) early in life is reno-protective and increases renal functional reserve (RFR) at 8 months of age. Here we investigated the long-term effects of brief early ACEi in SFK sheep out to 20 months of age. At 100 days gestation (term = 150 days) SFK was induced by fetal unilateral nephrectomy, or sham surgery was performed (controls). SFK lambs received enalapril (SFK+ACEi; 0.5 mg/kg, once daily, orally) or vehicle (SFK) from 4 to 8 weeks of age. At 8, 14 and 20 months of age urinary albumin excretion was measured. At 20 months of age, we examined basal kidney function and RFR via infusion of combined amino acid and dopamine (AA+D). SFK+ACEi resulted in lower albuminuria (∼40%) at 8 months, but not at 14 or 20 months of age compared with vehicle-SFK. At 20 months, basal GFR (∼13%) was lower in SFK+ACEi compared with SFK, but renal blood flow (RBF), renal vascular resistance (RVR) and filtration fraction were similar to SFK. During AA+D, the increase in GFR was similar in SFK+ACEi and SFK animals, but the increase in RBF was greater (∼46%) in SFK+ACEi than SFK animals. Brief ACEi in SFK delayed kidney disease in the short-term but these effects were not sustained long-term.

A congenital solitary functioning kidney (SFK) predisposes children to hypertension, albuminuria and kidney disease early in life [1,2]. Indeed, ∼26% of children with a SFK have hypertension by ∼5 years of age and ∼19% are diagnosed with proteinuria by ∼10 years of age [1]. In response to a reduction in kidney mass, glomerular hypertrophy and hyperfiltration initially normalize kidney function but over time may contribute to the pathophysiology of kidney disease [3].

Renal functional reserve (RFR) is the increase in glomerular filtration rate (GFR) from baseline induced by a vasodilatory stimulus (protein load, intravenous amino acid and/or dopamine infusion) [4]. A reduced RFR can occur in states of low nephron number with glomerular hyperfiltration despite GFR remaining within normal ranges [5]. Impaired RFR has been observed in hypertension [6], adult kidney donors [7], progressive kidney disease [8] and children with SFK [5].

Angiotensin converting enzyme inhibitors (ACEi) are efficient in reducing blood pressure (BP), proteinuria and risk of kidney disease progression in children with chronic kidney disease (CKD) [9,10]. In addition, ACEi at a critical window early in life has been shown to prevent the development of hypertension and improve kidney function in spontaneously hypertensive rats (SHR), a benefit that persists up to ∼16 months after treatment withdrawal [11,12]. We have recently shown that brief ACEi treatment from 4 to 8 weeks of age in an ovine model of SFK, delayed kidney hypertrophy and prevented albuminuria independent of BP lowering, 6 months after treatment withdrawal [13]. In addition, we found mitigation of glomerular hyperfiltration (lower GFR and filtration fraction), enhanced RFR and increased nitric oxide (NO) bioavailability [13], factors that are impaired in SFK sheep [14–16]. Taken together, these data indicate that modifying glomerular haemodynamics by early life ACEi in a sheep model of congenital SFK, with similar kidney development and maturation as humans, may preserve kidney lifespan. Therefore, in the present study, we followed a separate cohort of animals to 20 months of age to determine if the reno-protection persisted.

In the present study we examined whether ACEi (enalapril) from 4 to 8 weeks in SFK lambs (1) reduced albuminuria beyond 8 months of age, (2) reduced hyperfiltration (lower GFR and filtration fraction) at 20 months of age, (3) increased vasodilation of renal vasculature at 20 months of age, or (4) increased the RFR response to a combined infusion of amino acids and dopamine at 20 months of age, 18 months after treatment cessation.

Animals

An Animal Ethics Committee of Monash University approved experimental procedures (Ethics numbers: MARP/182/2016, #20442), which were performed in accordance with the guidelines of the National Health and Medical Research Council of Australia. All sheep were housed at the Monash University's Gippsland Field Station in between surgical/experimental procedures, and transported to Monash Animal Research Platform for surgical/experimental procedures. Surgical procedures were performed under isoflurane anesthesia, with a detailed description of the surgical and experimental procedures previously published [13]. Briefly, a congenital SFK was induced by unilateral nephrectomy in the sheep fetus on the 100th day of a 150-day gestation (SFK; n=19). A sham procedure was also performed (sham; n=9). Only male fetuses were used in the present study. SFK lambs aged 4 weeks were randomly assigned to undergo ACEi via oral administration of enalapril (maleate salt, E6888, 0.5 mg/kg/day; n=10; SFK+ACEi group) or vehicle (water; n=9; SFK group). At 6 months of age, lambs underwent surgery to construct carotid artery loops, allowing direct access to the carotid artery for catherization to measure blood pressure (BP) and collect blood samples. At 20 months of age sheep underwent surgery under general anesthesia for insertion of a bladder catheter as previously detailed [17] for the measurement of kidney function.

Kidney volume, basal cardiovascular and kidney function

At 2, 6 and 20 months of age kidney volume was determined by magnetic resonance imaging (MRI), via a three-dimensional T1 VIBE DIXON sequence with a Siemens Skyra (Siemens, Erlangen, Germany), as previously described [13]. At 8 and 14 months of age, sheep underwent a body fluid balance study where food and water intake and urine output were monitored, and 24-h urinary albumin excretion was determined over 5 days. At 8 and 14 months of age, BP (systolic, diastolic, mean) and heart rate (HR) were measured via an indwelling arterial catheter over a 72-h period. At 20 months of age, following surgical insertion of a bladder catheter and recovery, basal GFR and renal blood flow (RBF) were measured via 51Chromium ethylenediaminetetraacetic acid (51Cr EDTA) and para-aminohippuric acid (PAH) clearance, respectively, over a 7-h period with BP and HR measured continuously during this period. A 1-h urine sample collected in this basal period was used to determine albumin excretion (expressed as mg/24 h) at this age.

Cardiovascular and kidney function in response to amino acid and dopamine infusion

Response to combined amino acid and dopamine (AA+D) infusion was determined 2 days after basal cardiovascular and kidney function measurement. To establish baseline BP, HR and kidney function were measured for 60 min following one hour of equilibration. Then intravenous infusion of amino acids (0.065 ml/kg/hour of a 10% solution without electrolytes, Synthamin 17®, AHA692, Baxter) plus dopamine (5 μg/kg/min, dopamine hydrochloride, H8502, Sigma-Aldrich) was administered for 2 h. Within 2–3 days of experimentation, sheep were euthanized with an overdose of Pentobarbitone sodium (100 mg/kg, iv.).

Sample analysis

51Cr EDTA levels were measured via a gamma counter (PerkinElmer Wizard 1470). PAH concentration was determined using a previously described rapid microplate assay [18]. Plasma renin activity (PRA) was determined by radioimmunoassay (ProSearch International Pty, Malvern, Australia) from blood withdrawn via jugular vein puncture in lambs (4–8 weeks of age), which in the ACEi treated animals occurred approximately 1 h after treatment at each age, and arterial blood samples collected at 8, 14 and 20 months of age. Urinary albumin levels were assayed via an Albuwell O-ovine microalbuminuria ELISA kit (Exocell, 1013, Philadelphia, PA) as per manufacturer’s instructions. Urinary protein concentration was determined using the Pierce™ Coomassie (Bradford) protein assay kit (23236, ThermoFisher Scientific) and corrected for urine flow. Renal vascular resistance (RVR) was calculated as (MAP/RBF), and filtration fraction was calculated as (GFR/effective renal plasma flow). Urinary sodium excretion (UNAV) was measured (Beckman Coulter, Monash Medical Centre) and corrected for urine flow. Filtered load sodium was determined as (plasma sodium concentration × GFR), and fractional sodium excretion (FENA%) calculated as ([UNAV/filtered load sodium] × 100).

Tissue analysis

Kidneys were immersion fixed in 4% paraformaldehyde and paraffin embedded for histological analysis (Monash histology platform). Sections were blinded and assessment of fibrosis, glomerular diameter and kidney histopathology (assessed by expert pathologist H.B-O), were performed via Masson’s trichrome and Periodic acid–Schiff stains. Kidney histopathology was scored on the basis of pathology severity, assigned as follows: zero, no lesions apparent; one, minimal change; two, mild change; three, moderate change; four, marked/severe change(s) present.

Statistical analysis

All values are presented as mean ± SEM. Statistical analysis was performed using GraphPad Prism 9.0 (GraphPad software Inc., CA, U.S.A.), statistical significance was accepted as P≤0.05. Data were tested for normality using a Shapiro–Wilk test and for data that violated normality a rank-based test was performed. An analysis of variance was performed (body weight, kidney volume, MAP, HR, albumin) by fitting a mixed model ANOVA examining the effects of two factors: group (Pgroup; sham, SFK, or SFK+ACEi), age (Page) and their interaction (Pgroup×age). A two-way ANOVA was performed examining the effects of group (Pgroup; sham, SFK or SFK+ACEi) and AA+D (PAA+D; basal and during AA+D infusion) and their interaction. Basal kidney function variables, absolute change from baseline in response to AA+D, and kidney histopathology were analyzed by a one-way ANOVA, and where appropriate a Dunnett’s post-hoc analysis was performed (comparing with SFK group).

Plasma renin activity (PRA) early in life

PRA was similar between sham and SFK sheep at 4 and 8 weeks of age (Figure 1A). In SFK sheep, ACEi treatment significantly increased PRA (Figure 1B). Compared with pre-ACEi levels at 4 weeks of age, PRA was ∼267% greater at 5 weeks, ∼133% greater at 6 weeks, and ∼120% greater at 7 weeks but was not significantly different at 8 weeks of age (Figure 1B).

Body weights and kidney volume at 2, 6 and 20 months of age

Birth weight and body weights during the study were similar between groups (Figure 2A). Total kidney volume, presented as one or two kidneys for sham sheep and one kidney for SFK and SFK+ACEi sheep, increased with age in all groups (Page<0.0001, Figure 2B). Total kidney volume was significantly greater in SFK sheep (∼45–47%) than a single kidney of a sham and similar between sham (two kidneys), SFK and SFK+ACEi groups at 2, 6 and 20 months of age (Figure 2B). Total kidney volume normalized to body weight decreased with age in all groups (Page<0.0001, Figure 2C). At 2 months of age kidney volume normalized to body weight was ∼17% lower in the SFK group compared with sham (two kidney) counterparts and ∼40% greater compared with sham (one kidney) counterpart (both P<0.0001, Figure 2C). At the end of ACEi treatment (2 months of age) SFK+ACEi animals had a ∼13% lower normalized kidney volume compared with SFK animals (P=0.02, Figure 2C). At 6 months of age kidney volume normalized to body weight was ∼19% lower in SFK animals compared with sham (two kidneys) (P=0.001, Figure 2C) and ∼38% greater than sham (one kidney) (P<0.0001, Figure 2C), but similar between SFK and SFK+ACEi animals. At 20 months of age normalized kidney volume was ∼45% greater in SFK sheep compared with sham (one kidney) counterparts (P<0.0001) and similar between sham (two kidneys), SFK and SFK+ACEi groups (Figure 2B).

Basal mean arterial pressure (MAP), heart rate (HR), urinary albumin excretion and PRA at 8, 14 and 20 months of age

MAP was significantly higher in SFK sheep at all ages compared with sham (Pgroup<0.0001, Table 1). However, MAP was similar in SFK and SFK+ACEi groups at each age (Table 1). HR decreased with age (Page<0.0001, Table 1), but was similar between groups at each age. Urinary albumin excretion was significantly greater in SFK (∼47–155%) compared with sham animals at all ages (Table 1). At 8 months of age, urinary albumin was significantly lower (∼40%) in SFK+ACEi sheep compared with SFK (P=0.04, Table 1). However, urinary albumin excretion was not different between SFK+ACEi and SFK groups at 14 and 20 months of age (Table 1). Urine flow was similar between groups at all ages (Table 1). PRA declined with age in all groups (Page<0.0001, Table 1) and was significantly lower in SFK sheep compared with sham sheep at all ages (Pgroup<0.008, Table 1). PRA was similar between SFK+ACEi and SFK animals at all ages.

Basal kidney function at 20 months of age

At 20 months of age, SFK sheep had a significantly lower GFR (∼26%, P=0.04, Figure 3A) and RBF (∼23%, P<0.0001, Figure 3B) and greater renal vascular resistance (RVR) (∼55%, P<0.0001, Figure 3C). Filtration fraction was similar between SFK and sham sheep (Figure 3D). Compared with SFK sheep, SFK+ACEi sheep had a significantly lower GFR (∼13%, P=0.02, Figure 3A). However, RBF, RVR and filtration fraction were not different between SFK and SFK+ACEi sheep (Figure 3B–D).

Cardiovascular and kidney function in response to combined AA+D infusion at 20 months of age

AA+D infusion had no significant effect on MAP or HR in any group (Figure 4A,B). AA+D infusion caused RVR to decrease from baseline, which resulted in an increase in RBF and GFR in all groups (all PAA+D<0.0001, Figure 4C–E). Given the increase in RBF was greater than the increase in GFR, FF fell from baseline in all groups (PAA+D<0.0001, Figure 4F). In response to AA+D infusion the magnitude of the decrease in RVR and FF were similar between SFK and sham animals (Figure 4E,F). In the SFK group compared with sham animals, the increase in GFR (∼0.5 ml/min/kg less than sham, P=0.01, Figure 4C) and RBF (∼9.2 ml/min/kg less, P=0.0001, Figure 4D) were less in response to AA+D infusion. AA+D infusion caused a greater decrease in RVR (∼1.4 mmHg/ml/min/kg, P<0.0001, Figure 4E) and a greater increase in RBF (∼5.8 ml/min/kg, P=0.008, Figure 4D) in SFK+ACEi animals compared with SFK. However, the increment in GFR and reduction in FF were similar between SFK+ACEi and SFK animals (Figure 4C,F)

Kidney excretory function in response to combined AA+D infusion at 20 months of age

Urine flow, urinary protein excretion (both PAA+D<0.0001, Figure 4G,H), urinary sodium excretion (PAA+D = 0.0003, Figure 5A) and filtered load sodium (PAA+D<0.0001, Figure 5B) increased from baseline in all groups in response to AA+D infusion. AA+D infusion had no significant effect on fractional sodium excretion (Figure 5C). The magnitude of the increase in urine flow, urinary protein excretion and urinary sodium excretion were similar between groups. The magnitude of the increase in filtered load sodium was significantly less (∼102 μmol/ml/min, P=0.02) in SFK compared with sham animals and similar between SFK and SFK+ACEi animals (Figure 5B)

Post-mortem and kidney histopathology at 20 months of age

Body weight, kidney weight and kidney weight normalized to body weight were similar between groups (Table 2). Heart weight and heart weight normalized to body weight were significantly greater in SFK compared with sham animals, but similar between SFK and SFK+ACEi animals (Table 2). Mean glomerular diameter was significantly greater in SFK sheep compared with sham, an index of glomerular hypertrophy, but was similar between SFK+ACEi and SFK animals (Table 2). Percentage of cortical fibrosis was similar between groups. The overall pathology score, determined by an expert veterinary pathologist, was significantly greater in SFK compared with sham and similar between SFK+ACEi and SFK animals (Table 2).

The main finding of the present study was that a brief period of ACEi in early life reduced albuminuria in sheep born with a SFK at 8 months of age, confirming our earlier report [13], but this effect waned over time. However, residual differences in kidney function in adult SFK sheep remained 18 months following cessation of ACEi treatment. This included greater renal vasodilation in response to an AA+D infusion, though unlike our early study at 8 months of age, this was not sufficient to cause a greater increase in GFR. Significantly, at 20 months of age, GFR was lowered to a similar extent in the SFK+ACEi group as observed at 8 months of age [12]. Together these data indicate that brief early life ACEi has altered the trajectory of kidney disease in SFK, but future studies examining modification of the window and duration of ACEi treatment are required to establish if outcomes may be improved long-term.

In the present study, the prevention of albuminuria observed at 8 months of age in SFK sheep treated briefly with ACEi early in life was not sustained in the long-term with elevations in urinary albumin excretion having returned to SFK levels at 14 and 20 months of age. The degree to which albuminuria was reduced at 8 months of age mirrored our previous findings in a separate cohort of sheep [13]. Interestingly, in the ESCAPE trial in children with CKD and hypertension who received long-term ACEi, an early anti-proteinuric effect was followed by a gradual increase in proteinuria to pre-treatment levels after 3 years of follow-up despite blood pressure control [9]. In children with hypodysplastic CKD, it has been shown that continuous ACEi reduced blood pressure, but did not slow kidney functional decline. This may indicate ACEi in established CKD may not be effective in altering its course [19]. In the present study, brief early life ACEi in SFK did not prevent the elevation in blood pressure at 8, 14 or 20 months of age. Given blood pressure control is an important target to slow progression of kidney disease in children [9], the persistent elevation in blood pressure in SFK+ACEi animals may have contributed, at least in part, to the rebound in albuminuria observed by 14 months of age. In the Prague hypertensive rat, the long-term blood pressure lowering effects of brief treatment with losartan, from 5 to 9 weeks of age, were intensified by a second treatment window between 15 and 19 weeks of age [20]. Thus, modulation of treatment dose, window or regime in SFK sheep may prolong the reno-protective benefits and/or result in blood pressure lowering effects and, this needs to be examined in future studies.

In the present study, early life ACEi in SFK sheep resulted in ∼13% lower basal GFR than SFK sheep 18 months after withdrawal of ACEi. A similar reduction in GFR was seen between the groups at 8 months of age in our earlier study [13], which may suggest that CKD has not progressed over this period in either group. In our previous study, a lower GFR and a higher RBF resulted in a lower filtration fraction in SFK+ACEi compared with SFK sheep at 8 months of age [13]. This was accompanied by a lower albumin excretion in SFK+ACEi than SFK sheep, indicating a reduction in hyperfiltration-mediated injury. However, in the present study at 20 months of age, SFK+ACEi sheep had lower GFR than SFK but RBF, FF and albuminuria were similar between the groups. Taken together this suggests that the beneficial effects of early life ACEi in SFK on kidney hemodynamics wanes over time. This lower GFR at 20 months of age could be due to a reduction in ultrafiltration pressure, which would suggest differential regulation of renal segmental vascular resistances between the SFK and SFK+ACEi groups. Alternatively, the lower GFR in SFK+ACEi animals could be due to a reduction in glomerular ultrafiltration coefficient due to reduced hydraulic conductivity and/or reduced filtration surface area (FSA) [21,22]. However, a reduction in FSA seems unlikely given glomerular diameter and kidney volume (measured by MRI) were similar between SFK and SFK+ACEi animals. This sheep SFK model is associated with compensatory nephrogenesis, at 130 days of gestation nephron number was ∼45% more in the SFK compared with a single kidney of a sham sheep and nephrogenesis complete by birth as in humans [23–25]. This indicates that the increase in kidney volume in SFK and SFK+ACEI sheep is partly driven by an increase in nephron number and hypertrophy. There is variation in filtration fraction in the SFK+ACEi animals at 20 months of age, which may indicate that the response to brief early ACEi is waning at variable rates within the group. This is consistent with human studies where there is inter-individual variation in the protein lowering response to ACEi [26]. Whether this lower GFR observed in SFK+ACEi animals delays or accelerates the loss of kidney function compared to SFK sheep requires further investigation beyond 20 months of age. Collectively these observations indicate that that the reno-protective effects of this regimen of brief ACEi early in life are not sustained long-term in SFK.

In the present study, in response to AA+D the increase in GFR was similar between the SFK and SFK+ACEi groups, but SFK+ACEi sheep had a greater decrease in RVR and increase in RBF than SFK. It is possible that residual structural remodelling of the glomerular resistance vessels in the kidney by early life ACEi in SFK increased the capacity for vasodilation driving this response to AA+D [27]. The greater reduction in RVR in response to recruitment of functional reserve in the SFK+ACEi animals compared with SFK, may indicate that these animals maybe more susceptible to glomerular damage due to an increase in glomerular pressure during a physiological challenge. NO also plays an important role in the vasodilatory response to amino acid and/or dopamine infusion [28,29]. In this model of SFK, renal NO bioavailability, determined by total urinary nitrate and nitrite (NOx) excretion, is lower than in sham animals [14,30]. However, previous evidence suggests that urinary NOx excretion does not reflect acute changes in systemic and/or renal NO in response to physiological challenges that alter NO production [31]. Therefore, while not measured in the present study, it is possible that SFK+ACEi sheep have a greater capacity to generate NO in response to AA+D infusion, resulting in the greater increment in RBF compared with SFK sheep.

Systemic infusion of dopamine, at low doses, causes renal vasodilation via D1 [32] and D2-like receptors [33]. Stimulation of D1 receptors increases RBF without affecting GFR in the adult Wistar Kyoto rat but this vasodilation is blunted in the SHR counterpart [34]. However, pretreatment with an AT1R blocker, restores the RBF response and also increases GFR in SHR in response to D1 receptor stimulation [34]. In SHR and rats subjected to subtotal nephrectomy renal D1R dysfunction associated with receptor G-protein uncoupling occurs [35,36]. ATIR and D1R interact forming a heteromeric-signaling complex in the kidney with stimulation of one receptor preventing the signaling of the other [37]. Therefore, by reducing AT1R stimulation with ACEi during early life in SFK it is possible that D1R signaling was improved and still present 18 months after treatment withdrawal driving the greater renal vasodilatory response to AA+D. Future studies need to examine kidney hemodynamic responses to D1 receptor stimulation in SFK sheep and in response to ACEi in SFK to confirm this.

Strengths of this study include the similarity in timing of nephrogenesis in sheep and humans and that functional measurements were conducted in conscious sheep. Additionally, the dose of enalapril (0.05 mg/kg/day) used in the current study is similar to clinical doses of ACEi used in children with CKD [38]. Limitations of the present study include lack of blood pressure and renal function measurement at the end of the treatment window or any time before 8 months of age. ACEi likely decreased BP during the treatment window, as this has been reported previously in lambs [39], but it would be of interest to know if, and for how long, BP remained low after cessation of treatment. Serial measurement of kidney function could not be performed because of the difficulty of placing bladder catheters in male sheep. Thus, GFR measurements were limited to 20 months of age.

In conclusion, brief postnatal ACEi in SFK sheep delayed the onset of albuminuria by at least 8 months. However, the reno-protective benefits of early ACEi in SFK diminished with age. GFR was lower in SFK+ACEi animals compared with SFK 18 months after the withdrawal of treatment. But whether this lower GFR will delay or accelerate loss of kidney function requires further investigation. At 20 months of age, in response to AA+D although GFR and RBF increased in all groups, the increase in RBF was greater in the SFK+ACEi group than in SFK. This greater vasodilation of SFK vasculature may indicate some long-lasting kidney functional effects of brief ACEi early in life. Modulation of the window or duration of ACEi needs to be investigated to determine if sustained long term effects can be achieved to benefit children with SFK.

  • Onset of hypertension and kidney disease in children born with a solitary functioning kidney (SFK) can occur early in life as a result of hyperfiltration mediated injury. A brief period of angiotensin-converting enzyme inhibition (ACEi) early in life in sheep with SFK is reno protective at 8 months of age, but the long-term consequences of this treatment are unknown.

  • Reno-protective benefits of brief early ACEi in SFK waned with age with albuminuria similar to untreated levels by 14 months of age. But some residual changes in kidney hemodynamics remained at 20 months of age.

  • Brief postnatal ACEi alters the trajectory of kidney disease in SFK. A better understanding of the adaptation of kidney function due to this treatment and alterations in the duration of ACE inhibition to prolong benefits is required to improve long-term outcomes in children with SFK.

The data underlying this article will be shared on reasonable request to the corresponding author.

MFS has received consulting fees from Travere Therapeutics and Bayer.

M.F.S was supported by a grant from The Netherlands Organization for Health Research and Development (ZonMW Vidi 016.156.454). K.M.D. [grant number APP1041844] and K.M.M. [grant number APP1078164] are supported by Principal Research Fellowships from the National Health and Medical Council of Australia and Z.M was supported by an Australian Government Research Training Program Stipend Scholarship.

Open access for this article was enabled by the participation of Monash University in an all-inclusive Read & Publish agreement with Portland Press and the Biochemical Society under a transformative agreement with CAUL.

Zoe McArdle: Data curation, Formal analysis, Investigation, Visualization, Writing—original draft, Project administration. Reetu R. Singh: Conceptualization, Data curation, Formal analysis, Supervision, Validation, Investigation, Visualization, Methodology, Project administration, Writing—review & editing. Helle Bielefeldt-Ohmann: Formal analysis, Writing—review & editing. Karen M. Moritz: Conceptualization, Methodology, Writing—review & editing. Kate M. Denton: Conceptualization, Resources, Data curation, Formal analysis, Supervision, Funding acquisition, Validation, Visualization, Writing—review & editing. Michiel F. Schreuder: Conceptualization, Data curation, Supervision, Funding acquisition, Writing—review & editing.

The authors would like to thank Mr. Alan McDonald and Associate Professor Ross Young for assistance with surgeries and Mr. Bruce Doughton for technical assistance. The authors acknowledge the facilities and scientific and technical assistance of the National Imaging Facility (NIF), a National Collaborative Research Infrastructure Strategy (NCRIS) capability at Monash Biomedical Imaging (MBI), a Technology Research Platform at Monash University. We acknowledge the technical assistance of Dr. Michael de Veer and Mr. Richard McIntyre.

ACEi

angiotensin-converting enzyme inhibition

BP

blood pressure

CKD

chronic kidney disease

GFR

glomerular filtration rate

HR

heart rate

MAP

mean arterial pressure

NO

nitric oxide

PRA

plasma renin activity

RBF

renal blood flow

RFR

renal functional reserve

RVR

renal vascular resistance

SFK

solitary functioning kidney

1.
Westland
R.
,
Kurvers
R.A.
,
van Wijk
J.A.
and
Schreuder
M.F.
(
2013
)
Risk factors for renal injury in children with a solitary functioning kidney
.
Pediatrics
131
,
e478
e485
[PubMed]
2.
Sanna-Cherchi
S.
,
Ravani
P.
,
Corbani
V.
,
Parodi
S.
,
Haupt
R.
,
Piaggio
G.
et al.
(
2009
)
Renal outcome in patients with congenital anomalies of the kidney and urinary tract
.
Kidney Int.
76
,
528
533
[PubMed]
3.
McArdle
Z.
,
Schreuder
M.F.
,
Moritz
K.M.
,
Denton
K.M.
and
Singh
R.R.
(
2020
)
Physiology and pathophysiology of compensatory adaptations of a solitary functioning kidney
.
Front. Physiol.
11
,
[PubMed]
4.
Jufar
A.H.
,
Lankadeva
Y.R.
,
May
C.N.
,
Cochrane
A.D.
,
Bellomo
R.
and
Evans
R.G.
(
2020
)
Renal functional reserve: From physiological phenomenon to clinical biomarker and beyond
.
Am. J. Physiol.-Regulatory, Integrative Comparative Physiol.
319
,
R690
R702
[PubMed]
5.
Peco-Antić
A.
,
Paripović
D.
,
Kotur-Stevuljević
J.
,
Stefanović
A.
,
Šćekić
G.
and
Miloševski-Lomić
G.
(
2012
)
Renal functional reserve in children with apparently normal congenital solitary functioning kidney
.
Clin. Biochem.
45
,
1173
1177
[PubMed]
6.
Zitta
S.
,
Stoschitzky
K.
,
Zweiker
R.
,
Oettl
K.
,
Reibnegger
G.
,
Holzer
H.
et al.
(
2000
)
Dynamic renal function testing by compartmental analysis: assessment of renal functional reserve in essential hypertension
.
Nephrol. Dial. Transplant.
15
,
1162
1169
[PubMed]
7.
Figurek
A.
,
Luyckx
V.A.
and
Mueller
T.F.
(
2020
)
A systematic review of renal functional reserve in adult living kidney donors
.
Kidney Int. Rep.
5
,
448
458
[PubMed]
8.
Barai
S.
,
Gambhir
S.
,
Prasad
N.
,
Sharma
R.K.
and
Ora
M.
(
2010
)
Functional renal reserve capacity in different stages of chronic kidney disease
.
Nephrology (Carlton).
15
,
350
353
[PubMed]
9.
,
Group ET
Wuhl
E.
,
Trivelli
A.
,
Picca
S.
,
Litwin
M.
,
Peco-Antic
A.
et al.
(
2009
)
Strict blood-pressure control and progression of renal failure in children
.
N. Engl. J. Med.
361
,
1639
1650
[PubMed]
10.
van den Belt
S.M.
,
Heerspink
H.J.L.
,
Gracchi
V.
,
de Zeeuw
D.
,
Wühl
E.
and
Schaefer
F.
(
2018
)
Early proteinuria lowering by angiotensin-converting enzyme inhibition predicts renal survival in children with CKD
.
J. Am. Soc. Nephrol.
29
,
2225
2233
[PubMed]
11.
Harrap
S.B.
,
Mirakian
C.
,
Datodi
S.R.
and
Lever
A.F.
(
1994
)
Blood pressure and lifespan following brief ACE inhibitor treatment in young spontaneously hypertensive rats
.
Clin. Exp. Pharmacol. Physiol.
21
,
125
127
[PubMed]
12.
Harrap
S.B.
,
Nicolaci
J.A.
and
Doyle
A.E.
(
1986
)
Persistent effects on blood pressure and renal haemodynamics following chronic angiotensin converting enzyme inhibition with perindopril
.
Clin. Exp. Pharmacol. Physiol.
13
,
753
765
[PubMed]
13.
McArdle
Z.
,
Singh
R.R.
,
Bielefeldt-Ohmann
H.
,
Moritz
K.M.
,
Schreuder
M.F.
and
Denton
K.M.
(
2022
)
Brief Early Life Angiotensin-Converting Enzyme Inhibition Offers Renoprotection in Sheep with a Solitary Functioning Kidney at 8 Months of Age
.
J. Am. Soc. Nephrol.
33
,
1341
1356
[PubMed]
14.
Singh
R.R.
,
Easton
L.K.
,
Booth
L.C.
,
Schlaich
M.P.
,
Head
G.A.
,
Moritz
K.M.
et al.
(
2016
)
Renal nitric oxide deficiency and chronic kidney disease in young sheep born with a solitary functioning kidney
.
Sci. Rep.
6
,
26777
[PubMed]
15.
Lankadeva
Y.R.
,
Singh
R.R.
,
Moritz
K.M.
,
Parkington
H.C.
,
Denton
K.M.
and
Tare
M.
(
2015
)
Renal dysfunction is associated with a reduced contribution of nitric oxide and enhanced vasoconstriction after a congenital renal mass reduction in sheep
.
Circulation
131
,
280
288
[PubMed]
16.
Moritz
K.M.
,
Jefferies
A.
,
Wong
J.
,
Marelyn Wintour
E.
and
Dodic
M.
(
2005
)
Reduced renal reserve and increased cardiac output in adult female sheep uninephrectomized as fetuses
.
Kidney Int.
67
,
822
828
[PubMed]
17.
Singh
R.R.
,
Denton
K.M.
,
Bertram
J.F.
,
Jefferies
A.J.
and
Moritz
K.M.
(
2010
)
Reduced nephron endowment due to fetal uninephrectomy impairs renal sodium handling in male sheep
.
Clin. Sci. (Lond.)
118
,
669
680
[PubMed]
18.
Agarwal
R.
(
2002
)
Rapid microplate method for PAH estimation
.
Am. J. Physiol. Renal. Physiol.
283
,
F236
F241
[PubMed]
19.
Ardissino
G.
,
Viganò
S.
,
Testa
S.
,
Daccò
V.
,
Paglialonga
F.
,
Leoni
A.
et al.
(
2007
)
No clear evidence of ACEi efficacy on the progression of chronic kidney disease in children with hypodysplastic nephropathy—report from the ItalKid Project database
.
Nephrol. Dial. Transplant.
22
,
2525
2530
[PubMed]
20.
Heller
J.
and
Hellerová
S.
(
1998
)
Long-term effect on blood pressure of early brief treatment by different antihypertensive agents: a study in the prague hypertensive rat
.
Kidney Blood Press. Res.
21
,
445
451
[PubMed]
21.
Lenihan
C.R.
,
Busque
S.
,
Derby
G.
,
Blouch
K.
,
Myers
B.D.
and
Tan
J.C.
(
2015
)
Longitudinal study of living kidney donor glomerular dynamics after nephrectomy
.
J. Clin. Invest.
125
,
1311
1318
[PubMed]
22.
Maddox
D.A.
,
Bennett
C.M.
,
Deen
W.M.
,
Glassock
R.J.
,
Knutson
D.
,
Daugharty
T.M.
et al.
(
1975
)
Determinants of glomerular filtration in experimental glomerulonephritis in the rat
.
J. Clin. Invest.
55
,
305
318
[PubMed]
23.
Douglas-Denton
R.
,
Moritz
K.M.
,
Bertram
J.F.
and
Wintour
E.M.
(
2002
)
Compensatory renal growth after unilateral nephrectomy in the ovine fetus
.
J. Am. Soc. Nephrol.
13
,
406
410
[PubMed]
24.
Lankadeva
Y.R.
,
Singh
R.R.
,
Tare
M.
,
Moritz
K.M.
and
Denton
K.M.
(
2014
)
Loss of a kidney during fetal life: long-term consequences and lessons learned
.
Am. J. Physiol. Renal. Physiol.
306
,
F791
F800
[PubMed]
25.
Cochat
P.
,
Febvey
O.
,
Bacchetta
J.
,
Bérard
E.
,
Cabrera
N.
and
Dubourg
L.
(
2019
)
Towards adulthood with a solitary kidney
.
Pediatr. Nephrol.
34
,
2311
2323
[PubMed]
26.
van den Belt
S.M.
,
Heerspink
H.J.L.
,
Gracchi
V.
,
de Zeeuw
D.
,
Wühl
E.
and
Schaefer
F.
(
2018
)
Early proteinuria lowering by angiotensin-converting enzyme inhibition predicts renal survival in children with CKD
.
J. Am. Soc. Nephrol.
29
,
2225
2233
[PubMed]
27.
Bergström
G.
,
Johansson
I.
,
Stevenson
K.M.
,
Kett
M.M.
and
Anderson
W.P.
(
1998
)
Perindopril treatment affects both preglomerular renal vascular lumen dimensions and in vivo responsiveness to vasoconstrictors in spontaneously hypertensive rats
.
Hypertension
31
,
1007
1013
[PubMed]
28.
King
A.J.
,
Troy
J.L.
,
Anderson
S.
,
Neuringer
J.R.
,
Gunning
M.
and
Brenner
B.M.
(
1991
)
Nitric oxide: a potential mediator of amino acid-induced renal hyperemia and hyperfiltration
.
J. Am. Soc. Nephrol.
1
,
1271
1277
[PubMed]
29.
Tolins
J.P.
and
Raij
L.
(
1991
)
Effects of amino acid infusion on renal hemodynamics. Role of endothelium-derived relaxing factor
.
Hypertension
17
,
1045
1051
[PubMed]
30.
Singh
R.R.
,
McArdle
Z.M.
,
Booth
L.C.
,
May
C.N.
,
Head
G.A.
,
Moritz
K.M.
et al.
(
2021
)
Increase in bioavailability of nitric oxide after renal denervation improves kidney function in sheep with hypertensive kidney disease
.
Hypertension
77
,
1299
1310
[PubMed]
31.
Sütö
T.
,
Losonczy
G.
,
Qiu
C.
,
Hill
C.
,
Samsell
L.
,
Ruby
J.
et al.
(
1995
)
Acute changes in urinary excretion of nitrite + nitrate do not necessarily predict renal vascular NO production
.
Kidney Int.
48
,
1272
1277
[PubMed]
32.
Frederickson
E.D.
,
Bradley
T.
and
Goldberg
L.I.
(
1985
)
Blockade of renal effects of dopamine in the dog by the DA1 antagonist SCH 23390
.
Am. J. Physiol.
249
,
F236
F240
[PubMed]
33.
Luippold
G.
,
Osswald
H.
and
Mühlbauer
B.
(
1998
)
Renal effects of exogenous dopamine: modulation by renal nerves and dopamine receptor antagonists
.
Naunyn Schmiedebergs Arch. Pharmacol.
358
,
445
451
[PubMed]
34.
de Vries
P.A.
,
de Zeeuw
D.
,
de Jong
P.E.
and
Navis
G.
(
2004
)
The abnormal renal vasodilator response to D1-like receptor stimulation in conscious SHR can be normalized by AT1 blockade
.
J. Cardiovasc. Pharmacol.
44
,
571
576
[PubMed]
35.
Tapia
E.
,
García-Arroyo
F.
,
Silverio
O.
,
Rodríguez-Alcocer
A.N.
,
Jiménez-Flores
A.B.
,
Cristobal
M.
et al.
(
2016
)
Mycophenolate mofetil and curcumin provide comparable therapeutic benefit in experimental chronic kidney disease: role of Nrf2-Keap1 and renal dopamine pathways
.
Free Radic. Res.
50
,
781
792
[PubMed]
36.
Felder
R.A.
,
Kinoshita
S.
,
Ohbu
K.
,
Mouradian
M.M.
,
Sibley
D.R.
,
Monsma
F.J.
Jr
et al.
(
1993
)
Organ specificity of the dopamine1 receptor/adenylyl cyclase coupling defect in spontaneously hypertensive rats
.
Am. J. Physiol.-Regulatory, Integrative Comparative Physiol.
264
,
R726
R732
37.
Khan
F.
,
Špicarová
Z.
,
Zelenin
S.
,
Holtbäck
U.
,
Scott
L.
and
Aperia
A.
(
2008
)
Negative reciprocity between angiotensin II type 1 and dopamine D1 receptors in rat renal proximal tubule cells
.
Am. J. Physiol.-Renal Physiol.
295
,
F1110
F1116
[PubMed]
38.
Smeets
N.J.L.
,
Schreuder
M.F.
,
Dalinghaus
M.
,
Male
C.
,
Lagler
F.B.
,
Walsh
J.
et al.
(
2020
)
Pharmacology of enalapril in children: a review
.
Drug Discov. Today.
25
,
1957
1970
39.
Smith
F.G.
,
Chan
S.
and
Wildt
S.N.D.
(
1997
)
Effects of renal denervation on cardiovascular and renal responses to ACE inhibition in conscious lambs
.
J. Appl. Physiol.
83
,
414
419

Author notes

*

These authors contributed equally to this work.

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