INTRA-RENAL VASCULAR EFFECTS OF [DES-ASP1]ANGIOTENSIN-I AND ANGIOTENSIN-III IN THE DOG

The effects of direct renal intra-arterial injections of [des-Asp1(aspartate)]angiotensin I (0.2-3.2 .mu.g) and angiotensin III (0.00625-0.1 .mu.g) on renal blood flow was determined in 10 dogs anesthetized with pentobarbital. Both [des-Asp1]angiotensin I and angiotensin III caused dose-dependent decreases in renal blood flow. The decreases in ipsilateral renal blood flow occurred in the absence of changes in systemic arterial pressure and flow to the contralateral kidney, suggesting that the response was a local event. The renovascular responses to [des-Asp1]angiotensin I were attenuated during the i.v. administration of SQ 20881, a synthetic peptide that competitively inhibits angiotensin converting enzyme. SQ 20881 did not alter the vasoconstrictor responses to angiotensin III, angiotensin II or norepinephrine. [Ile7 (isoleucine)]angiotensin III (an angiotensin III antagonist) abolished decreases in renal blood flow produced by [des-Asp1]angiotensin I, angiotensin II, angiotensin III and angiotensin I but the response to norepinephrine was unchanged. Apparently the decrease in renal blood flow produced by [des-Asp1]angiotensin I is due to its local enzymatic conversion to angiotensin III. About 7% of [des-Asp1] angiotensin I is converted to angiotensin III during 1 transit through the kidney.