Intrarenal vascular resistance in glycerol-induced acute renal failure in the rat.

Abstract

Mean afferent arteriolar diameter and renal blood flow were measured with microsphere techniques in awake rats 24 h after induction of acute renal failure by glycerol injection. Renal blood flow, mean arterial pressure and total renal vascular resistance in rats with acute renal failure were not different from control levels, despite significantly elevated serum urea N. Mean afferent arteriolar diameter was decreased in rats with acute renal failure compared to controls (21.1 .+-. 0.10 vs. 22.0 .+-. 0.16 .mu.m, mean .+-. SE, n = 5, respectively, P < 0.01). The percentage of renal intravascular microspheres (mean diameter of spheres = 22.3 .+-. 2.1 .mu.m) entering the glomeruli also was decreased in rats with acute renal failure compared to control (75.9 .+-. 1.4 vs. 85.7 .+-. 0.8%, n = 7, respectively, P < 0.001). Blood viscosity values of rats injected with glycerol and measured at shear rates of 61.8/s [4.36 .+-. 0.06 centipoise (cP, n = 6] and 123.6/s [3.78 .+-. 0.05 cP, n = 6] were significantly higher than those of controls (3.84 .+-. 0.08 cP, n = 6, P < 0.005, and 3.36 .+-. 0.09 cP, n = 6, P < 0.005). Preglomerular resistance is increased during glycerol-induced acute renal failure due to a combination of afferent arteriolar vasoconstriction and increased blood viscosity. The increase in preglomerular resistance will cause a reduced glomerular capillary hydrostatic pressure in glycerol-induced acute renal failure.