1. The purpose of the present investigation was to determine whether an abnormality of the renal papillary circulation is present in a well-established model of cirrhosis without ascites (carbon tetrachloride/phenobarbital).
2. Compared with the control animals, cirrhotic rats showed a reduced diuretic (61.0 ±5.1 versus 18.0 ±2.5%) and natriuretic (67.8 ±8.3 versus 29.6 ±3.6%) response to a volume expansion (3% body weight infusion of 0.9% NaCl). The volume expansion-induced increase in renal interstitial hydrostatic pressure was also blunted in the cirrhotic rats (control 9.3 ±0.9 versus cirrhotic 6.1±1.0 mmHg) and there were no differences in mean arterial blood pressure, renal blood flow or glomerular filtration rate between control and cirrhotic animals.
3. Papillary plasma flow was determined by the 125I-albumin accumulation technique and expressed as mlmin−1100 g−1. In the basal state, papillary plasma flow was significantly lower in cirrhotic rats (59.1 ±4.4, n = 9) than in the control animals (81.8 ±6.9, n = 9). An isotonic saline expansion similar to the one described above significantly increased papillary plasma flow in control rats (108.4±9.1, n = 7) but did not change it in cirrhotic rats (60.2 ±4.9, n = 6).
4. Our results indicate the existence of a selective alteration in the renal papillary circulation in cirrhotic rats, both in the basal state and after a well-established vasodilatory stimulus. The reduced papillary plasma flow of the cirrhotic animals, probably mediated through changes in renal interstitial hydrostatic pressure, may participate in the sodium and water retention that precedes the development of ascites and may be an important mechanism mediating the blunted renal response to extracellular volume expansion.