An autoradiographic study of regional blood flow distribution in the rat kidney during ureteric obstruction--the role of vasoactive compounds.

Abstract

To determine the changes in regional renal blood flow during ureteric obstruction and to examine the role of vasoactive mediators in effecting these changes. Renal blood flow in Sprague-Dawley rats was assessed after periods of ureteric obstruction using a quantitative autoradiographic technique based on Kety's theory of diffusion of an inert tracer (14C-iodoantipyrine). Prostaglandins, thromboxanes and renin-angiotensin were inhibited pharmacologically using diclofenac sodium and enalapril. Baseline blood flow to the outer cortex, inner cortex and medulla was 807, 258 and 105 mL/100 g/min, respectively. There was an increase in outer cortical blood flow after 10 min of ureteric obstruction which became significant at 30 min (P < 0.05). There was a significant decrease in inner cortical and medullary blood flow at 30 min, to 210 and 68 mL/100 g/min, respectively (P < 0.05). Diclofenac sodium abolished the increase in outer cortical blood flow. After 24 h of unilateral ureteric obstruction, outer cortical blood flow decreased to 492 mL/100 g/min; inner cortical blood flow also decreased but to a lesser extent, to 190 mL/100 g/min. Inhibition of prostaglandins, thromboxanes and the renin-angiotensin system reduced the degree of renal vasoconstriction but there was still a significant decrease in outer cortical perfusion despite the presence of these blocking agents. The control of the renal vasculature involves a complex interplay between a variety of vasoactive mediators. Quantitative autoradiography offers the opportunity to evaluate changes in regional renal perfusion with high resolution and will allow a greater understanding of the pathophysiology of renal diseases.