Changes in angiotensin converting enzyme activity in the renal vascular bed of streptozotocin-induced diabetic rat

The purpose of this study was to look for evidence of changes in angiotensi n converting enzyme activity in the renal vascular bed of streptozotocin (S TZ)-induced diabetic rats. To assess the activity of the enzyme, we examine d angiotensin I- and angiotensin II-induced vasoconstriction in perfused ki dneys from controls and diabetic rats. Angiotensin I (3x10(-9) to 3x10(6) M ) induced a dose-dependent vasoconstriction in control kidneys; this respon se was completely inhibited by losartan (10(-5) M) and markedly inhibited b y both captopril (10(-4) M) and indomethacin (10(-5) M). Angiotensin II (10 (-10) to 3x10(-7) M) also caused a dose-dependent vasoconstriction in contr ol kidneys; this response was markedly enhanced by 10(-4) M L-NNA, and sign ificantly inhibited by losartan (10(-5) M). Angiotensin I-induced vasoconst riction was slightly greater in STZ-induced diabetic rats than in controls. but the maximal response was unaffected. These results suggest that angiot ensin I is rapidly converted to angiotensin II in the renal vascular bed, a nd that converting enzyme activity in the renal vascular bed may be decreas ed in STZ-induced diabetic rats.