Characterization of angiotensin pressor responses in the turtle Pseudemys scripta

Studies were conducted in turtles (Pseudemys scripta) to characterize vascular responses to administration of exogenous angiotensin [Asp1-Ile5]angiotensin II (AII). Marked pressor responses were present following AII administration (2 microgram/kg iv). The pressor response was completely blocked by concomitant administration of an analogue of AII, [Sar1-Ile8]AII. Both alpha-receptor blockade with phenoxybenzamine or catecholamine depletion by reserpine administration reduced the pressor response approximately 50%. Further treatment with [Sar1-Ile8]AII completely blocked the AII pressor response. We conclude that the pressor response to AII in this species that represents an ancient group of reptiles includes a catecholamine-dependent component and direct vascular receptors, both of which are sensitive to AII.