Renal vasoconstriction in glycerol-induced acute renal failure. Studies in the isolated perfused rat kidney.

1. Acute renal failure was produced in rats by the intramuscular injection of glycerol (6.1 mol/l 10 ml/kg). Either 2 or 4--6 h later the right kidney was isolated and perfused for 1 h with an electrolyte solution containing a gelatin preparation (Haemaccel, 35 g/l) at pressures between 90 and 100 mm Hg in a single-pass system. 2. In kidneys taken from rats with acute renal failure renal vascular resistance was markedly increased immediately after the start of the perfusion as compared with control kidneys taken from untreated rats. During the following 30 min of perfusion the resistance progressively decreased and, at 1 h of perfusion, was similar to that in control kidneys or only moderately elevated. 3. Despite the reduction of renal vascular resistance glomerular filtration rate was still markedly increased immediately after the start of the perfusion as compared with control kidneys taken from untreated rats. During the following 30 min of perfusion the resistance progressively decreased and, at 1 h of perfusion, was similar to that in control kidneys or only moderately elevated. 3. Despite the reduction of renal vascular resistance glomerular filtration rate was still markedly impaired after 1 h of perfusion and fractional reabsorption of sodium and water as well as the secretion of p-aminohippurate were diminished. Renal venous renin concentration and renin release were lower in kidneys taken from rats with acute renal failure than in the control experiments. 4. These results suggest that the increase in renal vascular resistance and the stimulation of renin release after injection of glycerol in vivo are the consequence of extra- rather than intra-renal mechanisms.

Effect of saralasin and serum in myohaemoglobinuric acute renal failure of rats.

1. In rats deprived of food and water for 24 h acute renal failure was produced by the intramuscular injection of glycerol. Eight hours later plasma urea concentration had increased threefold despite a small rise in urine volume. Plasma concentrations of renin and renin substrate were elevated. 2. When saralasin, a competitive antagonist of angiotensin II, was infused for 8 h after glycerol injection, urine volume and plasma urea were similar to values in rats that had received an infusion of saline. 3. Administration of rat serum (4.5 ml h-1 kg-1) for 4 h suppressed plasma renin concentrations, but plasma urea increased to the same extent as in rats without serum. 4. When saralasin and serum were infused at the same time, urine volume, urine osmolality and solute excretion increased and the rise of plasma urea was diminished. 5. Saralasin has a protective effect against glycerol-induced acute renal failure only when volume is replaced concomitantly.

Effects of saralasin on renal function of the rat.

In the isolated perfused rat kidney, saralasin inhibits the vasoconstrictor effect of angiotensin II in a dose-dependent manner. At high infusion rates saralasin, by itself, increases renal vascular resistance and supresses renin release. Such an agonistic effect is not observed in the presence of high concentrations of angiotensin II. In acute renal failure induced by glycerol, saralasin has a beneficial effect on urine volume, solute excretion and plasma urea concentration only when it is administered together with an adequate volume of rat serum.