Angiotensin converting enzyme inhibition and calcium antagonism attenuate streptozotocin-diabetes-associated mesenteric vascular hypertrophy independently of their hypotensive action

OBJECTIVESTo investigate the relative roles of angiotensin II, bradykinin, and calcium-dependent pathways in the genesis of mesenteric vascular hypertrophy in experimental diabetes. DESIGNStreptozotocin-induced diabetic Sprague–Dawley rats were randomly allocated to these treatments for 24 weeksno treatment; ramipril at a hypotensive dose; ramipril plus the bradykinin type 2 receptor blocker icatibant; icatibant alone; ramipril at a low dose; the angiotensin II type 1 receptor antagonist, valsartan; the dihydropyridine calcium antagonist, lacidipine; and the nondihydropyridine calcium antagonist mibefradil. METHODSSystolic blood pressure was serially measured every 4 weeks by tail-cuff plethysmography. We assessed the vascular architecture in sections of mesenteric arteries obtained after in-vivo perfusion, which were stained with an antibody to a-smooth muscle actin. RESULTSBoth blood pressure and the mesenteric arterial walllumen ratio were reduced by administration of ramipril, at the high dose, either alone or in combination with icatibant, and also by valsartan. Treatment either with the low dose of ramipril or with the calcium antagonists lacidipine and mibefradil was associated with a decrease in the walllumen ratio of the mesenteric arteries without influencing blood pressure. CONCLUSIONSThese findings demonstrate that blockade both of angiotensin II-dependent and of calcium-dependent pathways attenuates mesenteric vascular hypertrophy in experimental diabetes. Furthermore, the antitrophic effects of these antihypertensive agents may be independent of their hypotensive effects.