Alterations in vascular function and morphology in acute ischemic renal failure.

Left renal arteries of rats were clamped for 40 min, and the kidneys were studied 48 hr and 7 days following restoration of blood flow. At 48 hr, there was severe oliguria or anuria. Renal blood flow (RBF) was in the normal range, but there was a loss of RBF autoregulation between 95 to 120 mm of mercury in seven out of nine rats. Morphologically, arcuate and interlobular arteries and afferent arterioles showed focal, segmental necrosis of smooth muscle cells and diapedesis of red blood cells across their walls. At 7 days, renal function was still severely depressed. RBF showed a slight decrease that did not reach statistical significance, and RBF autoregulatory capacity was lost in 8 out of 11 rats. Morphologically, vascular lesions were characterized at this stage by marked thickening and fibrosis of the tunica adventitia of the interlobular arteries and afferent arterioles. Structural vascular alterations may impair smooth muscle contractile function and thus interfere with RBF autoregulatory function in this model of acute renal failure.