In this study we evaluated the effect of angiotensin(1-7) and its nonpeptide analog, AVE 0991, on the endothelial function in vivo. The experiments were performed in conscious adult male Wistar rats, with polyethylene catheters implanted into the descending aorta (through left carotid artery), for injection of acetylcholine or sodium nitroprusside, femoral artery for mean arterial pressure and heart rate measurement; and femoral vein for drug administration. Increasing doses of acetylcholine (3.1 ng to 25.0 ng) or nitroprusside (1.0 microg to 10.0 microg) were administered before and 30 minutes after the start of the infusion of: angiotensin(1-7) (0.7 and 7.0 pmol/min); A-779 (180 pmol/min); angiotensin(1-7) (7.0 pmol/min) combined with A-779 (180 pmol/min); AVE 0991 (11, 45, and 230 pmol/min); AVE 0991 (45 pmol/min) combined with A-779 (180 pmol/min), or vehicle (6 microL/min). Baseline mean arterial pressure and heart rate were not altered during angiotensin(1-7) or AVE 0991 infusion. Angiotensin(1-7) (0.7 pmol/min) infusion produced a significant potentiation of the hypotensive effect of acetylcholine (3.1 ng: -9+/-1 mm Hg before; -18+/-2 mm Hg after; P<0.05). A similar potentiation was observed with the higher dose of angiotensin(1-7). As observed for angiotensin(1-7), infusion of AVE 0991 at 230 pmol/min potentiated the acetylcholine effect (3.1 ng: -8+/-2 mm Hg before; -16+/-2 mm Hg after; P<0.05). The potentiating effect was not observed for nitroprusside. A-779 or l-NAME treatment blocked the potentiation produced by angiotensin(1-7) or AVE 0991. Our data indicate that short-term stimulation of angiotensin(1-7) receptors improve endothelial function through facilitation of nitric oxide release.