Specificity of arginine vasopressin and angiotensin II for microvessels in the hamster cheek pouch after the induction of renovascular hypertension.

The present study was undertaken to determine the specificity of the vasoconstrictor activity to angiotensin II (AII) and arginine vasopressin (AVP) on the microcirculation in normal and renovascular hypertensive states. Ten to fourteen days after the induction of hypertension, Syrian hamsters were anesthetized with pentobarbital sodium, the cheek pouch was exposed, and a plastic chamber was placed in situ so the membrane could be suffused with bicarbonate-buffered Ringer's solution (5% CO2, 95% N2, pH 7.4). Third order arterioles (30-45 micron) were identified for study and vessel diameter was measured using a shearing device. In one group of normotensive and hypertensive hamsters, AII was microapplied to the arteriole before and after adding an AVP antagonist to the suffusate. In a second group of similar hamsters, AVP was microapplied to the arteriole before and after adding an angiotensin II blocker, saralasin acetate, to the suffusate. AVP and AII receptor blockade was documented by observing whether the vasoconstrictor effect of either AVP or AII was abolished. Dose-response curves for either peptide were not altered in the presence of the antagonist to the other peptide; however, they were shifted to the left in the RHT hamsters. Neither AVP nor AII receptor blockade altered control resting arteriolar diameters. Thus, it can be concluded that the microvascular response to both AII and AVP are potentiated in RHT and there are no interactions between either AII or AVP with the receptors of the other peptide in these microvessels in normal or RHT hamsters, indicating a high specificity for each peptide to its vascular receptor.