Renal microvascular actions of angiotensin II fragments.

In the present study, we investigated renal microvascular responses to ANG-(1-7) and ANG IV. Diameter changes of small interlobular arteries, afferent arterioles, and efferent arterioles were assessed by using isolated perfused hydronephrotic rat kidneys. ANG-(1-7) and ANG IV concentration dependently decreased the diameters of all investigated renal microvessel, however, with a much lower potency than ANG II. The ANG II type 1 receptor blocker irbesartan completely reversed the responses to ANG-(1-7) and ANG IV, whereas the ANG II type 2 receptor blocker PD-123319 had no effect. Both ANG-(1-7) and ANG IV failed to alter renal microvascular constriction induced by ANG II. In addition, subnanomolar concentrations of ANG-(1-7) had no effect on the myogenic-induced tone of interlobular arteries and afferent arterioles. Thus our data indicate that at high concentrations, ANG-(1-7) and ANG IV are able to activate the ANG II type 1 receptor, thereby inducing renal microvascular constriction. The failure of ANG-(1-7) and ANG IV to reduce ANG II- and pressure-induced constrictions suggests that these fragments do not exert a vasodilator and/or ANG II antagonistic action in the kidney.