TRP (transient receptor potential) channels play important roles in the regulation of normal and pathological cellular function. In the vasculature, TRP channels are present both in ECs (endothelial cells) and vascular SMCs (smooth muscle cells) and contribute to vasomotor control mechanisms in most vascular beds. Vascular TRP channels are activated by various stimuli, such as mechanical perturbation, receptor activation and dietary molecules. Some of the specific roles of these channels in normal and impaired vascular function have emerged in recent years and include participation in vascular signalling processes, such as neurotransmission, hormonal signalling, NO production, myogenic tone and autoregulation of blood flow, thermoregulation, responses to oxidative stress and cellular proliferative activity. Current research is aimed at understanding the interactions of TRP channels with other vascular proteins and signalling mechanisms. These studies should reveal new targets for pharmacological therapy of vascular diseases, such as hypertension, ischaemia and vasospasm, and vascular proliferative states.

Asthma was originally thought to be associated with an intrinsic defect in β 2 ADR ( β 2 -adrenoceptor) function, tipping the balance towards parasympathetic bronchoconstriction. Hence β -blocking drugs (such as β 2 ADR antagonists and inverse agonists) may cause acute bronchoconstriction which, in turn, may be attenuated by anti-cholinergic agents. Although β 2 -agonists are highly effective for the acute relief of bronchoconstriction, their chronic use is accompanied by an adaptive reduction in β 2 ADR numbers and associated desensitization of response, resulting in increased exacerbations and rare cases of death. The hypothesis examined in the present article is that, while single dosing with a β -blocker may cause acute bronchoconstriction, chronic dosing may afford putative beneficial effects including attenuated airway hyper-responsiveness.

Penile erection is a complicated event involving the regulation of corpus cavernosal smooth muscle tone. Recently, the small monomeric G-protein RhoA and its downstream effector Rho-kinase have been proposed to be important players for mediating vasoconstriction in the penis. RhoA/Rho-kinase increases MLC (myosin light chain) phosphorylation through inhibition of MLCP (MLC phosphatase) thereby increasing Ca 2+ sensitivity. This review will outline the RhoA/Rho-kinase signalling pathway, including the upstream regulators, guanine nucleotide exchange factors, GDP dissociation inhibitors and GTPase-activating proteins. We also summarize the current knowledge about the physiological roles of RhoA/Rho-kinase in both male and female erectile tissues and its aberrations contributing to erectile dysfunction in several disease states. Understanding the RhoA/Rho-kinase signalling pathway in the regulation of erection is important for the development of therapeutic interventions for erectile dysfunction.

Triptans are agonists at 5-HT 1B and 5-HT 1D (where 5-HT is 5-hydroxytryptamine; serotonin) receptors and cause vasoconstriction of isolated blood vessels. The aim of the present study was to determine vasoconstrictor potency (EC 50 ) of triptans in human coronary and cerebral arteries and to examine whether there was any relationship with the maximal plasma concentrations ( C max ; nM) of the drugs achieved following oral administration of clinically relevant doses to man using values reported in the literature. We also examined the expression of 5-HT 1B receptors in atherosclerotic and normal coronary arteries. The vasocontractile responses to sumatriptan, rizatriptan or eletriptan were characterized by in vitro pharmacology. The ratio of C max /EC 50 was calculated. 5-HT 1B and 5-HT 1D receptors were visualized by immunohistochemical techniques in coronary arteries. Sumatriptan, rizatriptan and eletriptan were powerful vasoconstrictors in cerebral artery. The rank order of agonist potency was eletriptan=rizatriptan=sumatriptan. In the coronary artery, the triptans were weaker vasoconstrictors. The rank order of potency was similar. In cerebral artery the ratio of C max /EC 50 was not significantly different from unity, indicating a relationship between these two parameters. In general for the coronary artery, the ratios were significantly less than unity, indicating no direct relationship. Immunohistochemistry showed expression of 5-HT 1B receptors in the medial layer, but did not reveal any obvious difference in 5-HT 1B receptor expression between normal and atherosclerotic coronary arteries. The results support the notion that triptans are selective vasoconstrictors of cerebral arteries over coronary arteries and that there is a relationship between vasoconstrictor potency in cerebral arteries and clinically relevant plasma levels.

17β-Oestradiol (E 2 ; oestrogen) is known to increase endothelium-dependent vasodilatation and NO (nitric oxide) production. It is also known to decrease the response of VSMCs (vascular smooth muscle cells) to vasoconstrictors in vitro . E 2 induces a decrease in age-related BP (blood pressure) development in MSHR (male spontaneously hypertensive rats). Whether this decrease is due to an effect on the endothelium or smooth muscle is unknown. To determine this effect, we examined the role of E 2 on vascular endothelium and smooth muscle separately. We treated MSHR with E 2 (2 mg·kg -1 of body weight·week -1 ) for 5–7 weeks and then examined the vasoconstrictor response in the intact and denuded rings (with or without endothelium respectively). SBP (systolic BP) was measured weekly. Aortic cGMP and cAMP contents, aortic vasoconstrictor response, endothelium suppression of the vasoconstrictor response and basal NO release from aortic rings were all measured at the end of the study. We found that the age-related development of SBP in MSHR was decreased in E 2 -treated rats. The vascular response of denuded rings to a vasoconstrictor (phenylephrine and KCl) was increased in E 2 -treated rats; however, this phenomenon was masked in intact rings. The enhanced endothelial function appears to override the E 2 -increased smooth muscle vasoconstrictor response. Endothelium suppression, NO release and aortic cGMP content were all significantly higher in E 2 -treated rats than in controls. Thus our results suggest that E 2 improves endothelium function; furthermore, the accompanied NO/cGMP increase and the endothelium suppression may be associated with an E 2 -induced BP-lowering effect in MSHR.

Local drug delivery by coronary stents is of current research interest. Organ culture of human vascular tissue is a model of intimal hyperplasia. We report an ex vivo organ culture model of stented vessels. This allows stent–artery interactions to be studied in living tissue. The recognized anti-restenosis agent paclitaxel was chosen to test the organ culture model. Mammary artery specimens were cultured ‘closed’ (i.e. without opening them flat) for 72h. Phosphocholine-coated stents, half of them loaded with the anti-restenosis drug paclitaxel, were implanted. The absorption and elution characteristics of paclitaxel were established. Artery tissue remained viable at 72h when cultured closed, despite stent implantation. Specimens developed smooth muscle cell proliferation. The stents absorbed up to 127±29 μ g of paclitaxel, with a biphasic elution curve. A mean of 13% of the absorbed paclitaxel remained after a 24h perfusion. In mammary artery, these paclitaxel stents reduced or abolished smooth muscle cell proliferation compared with controls. This model allows the effects of stenting on human arterial tissue to be studied for at least 72h, long enough to demonstrate effects on smooth muscle cell proliferation. Phosphocholine-coated stents absorb adequate doses of paclitaxel, which is eluted gradually, inhibiting muscle cell proliferation. Such an organ culture model of stented mammary artery will provide useful data in addition to that from animal or cell culture models of drug-eluting stents.

Although the pathophysiology of critical limb ischaemia is poorly understood, there is evidence that the condition of the small arteries may determine the outcome of revascularization procedures. This study was designed to investigate the effects of critical limb ischaemia on the structure and function of the small arteries in the leg. Small arteries (< 500 μ m) from proximal (non-ischaemic) and distal (ischaemic) sites were obtained from patients undergoing bypass surgery for critical limb ischaemia and mounted in a myograph. Reactivity and morphological measurements were carried out and compared with controls. Control vessels from the thigh and calf showed no difference in media to lumen ratio. However, a comparison of ischaemic and non-ischaemic vessels from the patients with critical limb ischaemia showed significant thinning of the ischaemic vessel wall. Contraction studies using noradrenaline and angiotensin II revealed a significant decrease in the response of ischaemic vessels compared with the non-ischaemic vessels from the same patient. Moreover, these differences in reactivity were still apparent after the responses were corrected for wall thickness. Endothelial function assessed using the endothelium-dependent agonists acetylcholine and bradykinin showed a significantly impaired relaxation response to acetylcholine but not to bradykinin in the ischaemic vessels, and acetylcholine-induced relaxation was not improved after incubation with indomethacin. There was no change in the response to the endothelium-independent cAMP-mediated vasodilator iloprost but a significant impairment to sodium nitroprusside which acts via cGMP. These results suggest that small arteries in critical limb ischaemia are altered in both structure and function, with vessel wall thinning and impaired responses to acetylcholine and sodium nitroprusside.

1. We investigated the glomerular expression of three types of myosin heavy-chain isoforms, including S-myosin heavy-chain 40 (SM1), S-myosin heavy-chain 29 (SM2) and FS-myosin heavy-chain 34 (SMemb) in puromycin aminonucleoside nephrosis. 2. There was little change in SM1 and SM2 mRNA levels throughout the experiment. In contrast, glomerular SMemb mRNA increased on days 2 and 4 (before and soon after the onset of proteinuria, respectively), but declined on day 8 (the peak of proteinuria) . 3. Histological myosin heavy-chain expression was examined using three antibodies against SM1, SM2 and SMemb. Immunohistochemically, SM1 and SM2 were absent in the glomeruli associated with puromycin aminonucleoside nephrosis until day 20. The SMemb isoform was barely detectable in normal glomeruli, but substantial amounts of SMemb were demonstrated in the glomeruli of rats with puromycin aminonucleoside nephrosis. In the puromycin aminonucleoside-treated rats, the number of SMemb-positive glomerular cells increased on days 2 and 4. 4. We examined whether levels of α-smooth-muscle actin or proliferating cell nuclear antigen correlated with myosin heavy-chain levels in the glomeruli of rats with puromycin aminonucleoside nephrosis. None of the cellular components in the glomeruli was positive for either α-smooth-muscle actin or proliferating cell nuclear antigen in puromycin aminonucleoside nephrosis. 5. Administration of methylprednisolone to puromycin aminonucleoside-treated rats resulted in the rapid disappearance of proteinuria. However, methylprednisolone did not affect SMemb mRNA or immunostaining in the glomeruli of rats with puromycin aminonucleoside nephrosis. 6. These data suggest that SMemb may be a molecular marker for phenotypic change in early glomerular injury, and demonstrate that SMemb regulation differs from that of SM1, SM2, α-smooth-muscle actin and proliferating cell nuclear antigen in the glomeruli of rats with puromycin aminonucleoside nephrosis.

1. Bronchial responsiveness to inhaled methacholine was studied in ten heart-lung transplant (HLT) recipients a mean 10.6 months (range 1.5–28 months) post-HLT and in ten normal subjects. 2. The mean provocation dose of methacholine producing a 20% fall in FEV 1 (PD20 FEV 1 ) was significantly lower in the HLT recipients (1.70 ± 3.96 mg vs 11.55 ± 3.79 mg; P < 0.001), as was the mean provocation dose of methacholine producing a 50% fall in specific airway conductance (PD50 s G AW) (0.08 ± 0.08 mg vs 5.13 ± 5.47 mg; P < 0.005). 3. These results establish the presence of significant bronchial hyper-responsiveness to inhaled cholinergic agonists in the transplanted lung.

1. The contractile response to histamine, acetylcholine (ACh), KCl or electrical field stimulation (EFS) was examined in paired tracheal rings (one of each being denuded by mucosal rubbing), which were mounted in muscle chambers filled with a continuously aerated physiological salt solution at 37°C. 2. Removal of the respiratory mucosa increased the sensitivity of airway muscle to ACh, histamine and EFS, but not to KCl. The hypersensitivity of denuded rings to histamine and EFS was greater than to ACh. Atropine reduced the histamine hypersensitivity observed. 3. Pretreating intact preparations with indomethacin augmented their responsiveness to EFS, histamine and ACh. 4. Indomethacin augmentation of histamine- and EFS-induced responses was greater in preparations without epithelium. 5. We conclude that the airway mucosa may be associated with a factor that reduces airway smooth muscle responsiveness to stimulation.

1. We propose the following model of Ca 2+ mobilization by noradrenaline in vascular smooth muscle. Upon receptor occupation Ca 2+ from a labile small intracellular store on the inner plasmalemma is released. This Ca 2+ does not function as activator Ca 2+ but triggers Ca 2+ release from the sarcoplasmic reticulum (Ca 2+ -induced Ca 2+ release). 2. Simultaneously Ca 2+ from an extracellularly bound store (on the external surface of the plasmalemma) is dislodged, which enters the cell through receptor linked channels. 3. These processes are responsible for the early ‘phasic’ component of the noradrenaline contraction. In addition, Ca 2+ from the free extracellular Ca 2+ pool enters through receptor operated channels, supporting the maintained tension development.

1. The effects of varying [Ca 2+ ] o on the contraction of smooth muscle by different α-adrenoceptor agonists were examined on rat isolated anococcygeus muscle. Agonists were tested in the presence of various [Ca 2+ ] o or ‘Ca 2+ -re-addition curves’ were constructed. In some experiments the [Ca 2+ ] free was buffered with EGTA and nitrilotriacetic acid. The components of the response which were revealed were further analysed by using drugs which modify Ca 2+ mobilization. 2. Three separate elements in the contractile response were identified: (i) an initial transient contraction, due to intracellular Ca 2+ release could be isolated with [Ca 2+ ] o between 1 nmol/l and 3 μmol/l (this could be obtained only with noradrenaline, phenylephrine and amidephrine); (ii) a nifedipine-sensitive response requiring [Ca 2+ ] o of 3 μmol/l or more; (iii) a nifedipine-resistant response requiring [Ca 2+ ] o of 100 μmol/l or more. Presumably (ii) and (iii) involve the entry of Ca 2+ o : they could be obtained with all agonists tested, including these above, methoxamine, indanidine and xylazine. 3. The results are discussed in relation to the possibility of distinct types of response and their relationship to subgroups of receptors or agonists. It is concluded that there is a continuous spectrum of activity across the agonist range and that this is likely to correlate with ‘efficacy’ at a single α 1 receptor type.

1. The effect of a small increase in local plasma calcium concentration on the responsiveness of the forearm resistance vessels to verapamil has been examined in normal subjects, by using a plethysmographic method with infusion of calcium and other agents into the brachial artery. 2. Infusion of calcium at a rate which increased the concentration in forearm venous blood by about 0.5 mmol/l caused basal blood flow to fall by 19% and the dilator response to verapamil to fall by 35% ( n = 8; P <0.02). 3. When, after 46 min, the infusion of calcium was discontinued, the dilator response to verapamil increased to reach a level 53% higher than the initial control ( n = 8; P <0.02). 4. Infusion of calcium had no effect on the dilator response to sodium nitroprusside. 5. Infusion of noradrenaline at a rate which caused a greater reduction in basal flow than that induced by calcium had no effect on the response to verapamil. 6. It is concluded that the dilator response to verapamil, which is thought to reflect activity of the potential operated system for calcium entry, is selectively depressed by a small elevation of plasma calcium concentration, but subsequently becomes elevated. These findings point to an important role for calcium in the regulation of membrane function in the resistance vessels and support the view that altered calcium handling may contribute to the development of primary hypertension.

1. Transmembrane potentials ( E m ) of vascular muscle cells in caudal arteries in vitro from one-kidney, one-clip hypertensive and one-kidney, sham-clipped normotensive rats were measured. 2. The E m recorded in hypertensive rats was significantly lower (depolarized) than that recorded in normotensive control rats. 3. Boiled plasma supernatants from hypertensive rats depolarized the muscle cells in normotensive caudal artery but had no effect on muscle cells in arteries from hypertensive rats. 4. Boiled plasma supernatants from normotensive control rats had no effect on the E m of either animal. 5. Ouabain depolarized muscle cells of the normotensive artery only and the magnitude of depolarization induced was nearly the same as that produced by the supernatant from the hypertensive animals. 6. These data suggest that a ouabain-like humoral substance may play a role in the pathophysiology of one-kidney, one-clip hypertension through a voltage-dependent mechanism.

1. Calcium reactivity of arterial smooth muscle and the effect of diltiazem (calcium antagonist) were investigated in helical strips of mesenteric arteries from 6-week-old male spontaneously hypertensive rats (SHR) and age-and sex-matched normotensive Wistar-Kyoto (WKY) rats. Blood pressure was 130 ± 5 mmHg for SHR and 110 ± 5 mmHg for WKY rats (means ± sd ). 2. At high Ca 2+ concentration (3 × 10 −4 to 3 × 10 −3 mol/l) the calcium-induced tension of mesenteric arterial strips per cross-sectional area was significantly greater in SHR than in WKY rats in noradrenaline (10 −5 mol/l)-containing solution or in high K + (121 mmol/l) solution ( P < 0.001). At low Ca 2+ concentration (10 −5 mol of noradrenaline/l and 3 × 10 −5 mol/l in high K + ), the tension was smaller in SHR strips than in WKY rat strips ( P < 0.05). 3. The Ca 2+ sensitivity of SHR strips was significantly lower than that of WKY strips in noradrenaline-containing solution or in high K + solution. 4. Diltiazem, a calcium antagonist, shifted the dose-response curve of Ca 2+ -induced tension to the right equally in SHR and WKY rat strips. The inhibition of the maximum tension by the drug was greater in SHR strips than in WKY rat strips in noradrenaline-containing solution, but there was no difference in high K + solution. 5. The results suggest that the contractile abnormality might be a possible cause of hypertension in SHR.

1. The response of the forearm resistance vessels to local intra-arterial infusion of verapamil and sodium nitroprusside has been assessed by a plethysmographic method in 23 men with normal arterial pressure and 35 men with primary hypertension. 2. In the 20 patients with hypertension for whom full dose—response curves were determined, the dilator response to verapamil was significantly greater than that in the normal controls, whereas the response to sodium nitroprusside was reduced. 3. Comparison of responses to the two dilators in individual subjects enabled the scattering effect of variables common to both drugs to be reduced. Analysis of the results in this way showed a highly significant difference between the hypertensive men as a whole and the normotensive controls ( P < 0.00001); 24 out of the 35 hypertensive men showed responses that were outside the normal range. 4. The abnormal pattern of response observed in the hypertensive group cannot be accounted for by structural changes in the vessels and strongly suggests a functional abnormality of the vascular smooth muscle.

1. The response of arterial smooth muscle to noradrenaline was studied in one-clip hypertensive rats with or without the contralateral/kidney and in normotensive rabbits. 2. Strips of aorta from one-kidney, one-clip hypertensive animals were less responsive to noradrenaline than normotensive control rats. The contractile response of strips from two-kidney, one-clip hypertensive animals was not different from the control group. These results suggest that the mechanisms responsible for the lesser reactivity in the one-kidney hypertensive group are not a consequence of elevated blood pressure itself, but may be related to the intrinsic contractility of aortic smooth muscle. 3. Tonin potentiated the contraction induced by noradrenaline in aortic strips from hypertensive and normotensive rats. However, this effect was more important in the one-kidney, one-clip hypertensive animals. In the aortic and mesenteric strips from normal rabbits, tonin produced not only potentiation to noradrenaline but direct contraction. 4. The potentiation to noradrenaline and the direct effect of tonin were not affected by a variety of antagonists but were blocked by a calcium ion antagonist, verapamil, suggesting that tonin may act directly on vascular smooth muscle through mechanisms which might be mediated by calcium ions.

1. The ability of isolated membrane fractions of cardiomyocytes, aortic smooth muscle and erythrocytes from spontaneously hypertensive rats to bind calcium was investigated isotopically. 2. Plasma membranes of aortic smooth muscle and erythrocytes of spontaneously hypertensive rats possess a lower calcium-binding ability than preparations from normotensive controls. 3. Sarcoplasmic reticulum from the myocardium of spontaneously hypertensive rats had a lower ability to accumulate calcium. 4. Changes in the calcium-binding ability of the erythrocyte membrane of spontaneously hypertensive rats was related to the diminution of the amount of exchangeable calcium on the inner part of the membrane. The latter may be the cause of the increase of erythrocyte membrane permeability for sodium in spontaneously hypertensive rats and in patients with essential hypertension.

1. Structural and functional changes resulting from baroreceptor denervation were studied in rabbits 4 days after surgery. 2. After section of the aortic and carotid sinus nerves, arterial pressure was characteristically labile although the mean pressures were not significantly different from those of control animals. 3. The responsiveness of isolated ear arteries and cephalic veins from deafferented animals to noradrenaline and electrical stimulation of their sympathetic innervation was similar in both groups. 4. Neuronal uptake of noradrenaline into arterial tissue was similar in both groups, although uptake into the cephalic veins of deafferented animals was less than in the control group. 5. [ 3 H]Thymidine uptake, an index of DNA synthesis, was similar in both groups, radioautography revealing no difference in smooth muscle cell labelling. 6. Uptake of [ 3 H]proline, an indicator of protein synthesis, by aorta, ear, brachial, basilar and renal arteries from deafferented animals was greater than in control animals. 7. Baroreceptor denervation altered protein metabolism in the arterial wall.

1. Spiral strips of human digital arteries have been studied in vitro to investigate whether dl-propranolol, d-propranolol, oxprenolol and labetalol have peripheral vascular effects in man. 2. Labetalol was a potent inhibitor of contractile responses to noradrenaline, but had less effect on responses to 5-hydroxytryptamine and barium chloride. 3. dl-and d-propranolol were equally effective inhibitors of responses to barium chloride. They were only weak antagonists of noradrenaline responses, but stronger, non-competitive antagonists of 5-hydroxytryptamine responses. 4. Oxprenolol was only a weak inhibitor of the responses to both noradrenaline and 5-hydroxytryptamine and had little effect on responses to barium chloride. 5. It is concluded that labetalol has specific α-adrenoreceptor-blocking properties, which are probably relevant to its therapeutic action in man. Propranolol has non-specific inhibitory effects on vascular smooth muscle, which might contribute to its hypotensive activity at high concentrations, but oxprenolol has only slight peripheral effects that are probably therapeutically insignificant.

1. Intracellular concentrations of adenosine 3′: 5′-cyclic phosphate (cyclic AMP) and activities of adenylcyclase and phosphodiesterase were determined in oestrogen-pretreated rat uteri during exposure to different concentrations of angiotensin II. 2. No significant variations in cyclic AMP or in the enzyme activities were observed at concentrations of angiotensin inducing significant contractions. 3. It is concluded that in rat uterus, the process of excitation-contraction coupling triggered by angiotensin is not mediated by variations in intracellular levels of cyclic AMP.