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RENAL HEMODYNAMICS AND CARDIORENAL INTEGRATION

ANG II type 2 receptors and neural control of intrarenal blood flow

Departments of ¹Physiology and ²Pharmacology, Monash University, Victoria, Australia

Submitted 14 March 2006 ; accepted in final form 19 July 2006

We tested the hypothesis that activation of angiotensin type 2 (AT₂) receptors, by both exogenous and endogenous ANG II, modulates neurally mediated vasoconstriction in the renal cortical and medullary circulations. Under control conditions in pentobarbital-anesthetized rabbits, electrical stimulation of the renal nerves (RNS; 0.5–8 Hz) reduced renal blood flow (RBF; –88 ± 3% at 8 Hz) and cortical perfusion (CBF; –92 ± 2% at 8 Hz) more than medullary perfusion (MBF; –67 ± 6% at 8 Hz). Renal arterial infusion of ANG II, at a dose titrated to reduce RBF by 40–50% (5–50 ng·kg^–1·min^–1) blunted responses of MBF to RNS, without significantly affecting responses of RBF or CBF. Subsequent administration of PD123319 (1 mg/kg plus 1 mg·kg^–1·h^–1) during continued renal arterial infusion of ANG II did not significantly affect responses of RBF or CBF to RNS but enhanced responses of MBF, so that they were similar to those observed under control conditions. In contrast, administration of PD123319 alone blunted responses of CBF and MBF to RNS. Subsequent renal arterial infusion of ANG II in PD123319-pretreated rabbits restored CBF responses to RNS back to control levels. In contrast, ANG II infusion in PD123319-pretreated rabbits did not alter MBF responses to RNS. These data indicate that exogenous ANG II can blunt neurally mediated vasoconstriction in the medullary circulation through activation of AT₂ receptors. However, AT₂-receptor activation by endogenous ANG II appears to enhance neurally mediated vasoconstriction in both the cortical and medullary circulations.

kidney medulla; renal circulation; renin-angiotensin system; sympathetic nervous system

This article has been cited by other articles:

				S. L. Burke, G. A. Head, G. W. Lambert, and R. G. Evans Renal Sympathetic Neuroeffector Function in Renovascular and Angiotensin II-Dependent Hypertension in Rabbits Hypertension, April 1, 2007; 49(4): 932 - 938. [Abstract] [Full Text] [PDF]