Intrarenal Vascular Effects of Angiotensin II and Angiotensin III in the Dog

Abstract

The effects of intrarenal bolus injections of equal molar doses of angiotensin II and angiotensin III on renal blood flow were examined in seven pentobarbital anaesthetized dogs. Renal blood flow was measured with an electromagnetic flow probe. Angiotensin II produced a greater decrease in renal blood flow than angiotensin III at all bolus doses tested when the integral of the renal blood flow response was examined. In 10 other dogs, we compared the molar dose of intrarenal constant infusions of angiotensin II and angiotensin III required to decrease total renal blood flow by approximately 25%. The effect these peptides had on the distribution of renal cortical blood flow was determined with radioactive microspheres. In the constant infusion experiments, more moles of angiotensin III than angiotensin II were required to produce a given decrease in renal blood flow in each experiment. The average percent decrease in blood flow to each of the four cortical zones produced by angiotensin II was not different from that produced by angiotensin III. Our data demonstrate that angiotensin II is more potent than angiotensin III as a vasoconstrictor in the renal vasculature.