Control of renal medullary blood flow by vasopressin v1 and v2 receptors. Nakanishi, Kazushige, David L. Mattson, Volkmar Gross, Richard J. Roman, and Allen W. Cowley, Jr. Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226
APStracts 2:0027R, 1995.
Experiments were performed in anesthetized, renal denervated rats to determine the contribution of renal medullary vasopressin V1 and V2 receptor stimulation in the regulation of renal medullary blood flow. Renal medullary interstitial infusion of the selective V1 agonist [Phe2,Ile3,Orn8]-Vasopressin (2 ng/kg/min) significantly decreased outer medullary blood flow by 15% and inner medullary blood flow by 35% as measured with implanted optical fibers for laser -Doppler flowmetry. Medullary interstitial infusion of equimolar doses of AVP also decreased outer medullary blood flow by 15% but only decreased inner medullary blood flow by 17%, a decrease significantly less than the decrease observed during the infusion of the V1 agonist. These results were confirmed in videomicroscopy experiments on the exposed papilla which demonstrated that both the V1 agonist and AVP decreased descending and ascending vasa recta capillary red blood cell velocity and calculated blood flow with greater decreases observed during infusion of the V1 agonist. In further laser-Doppler flowmetry studies, it was demonstrated that stimulation of V2 receptors by medullary interstitial infusion of either DDAVP (2 ng/kg/min) or AVP in rats pretreated with the vasopressin V1 receptor antagonist d(CH2)5[Tyr(Me)2,Ala-NH2]AVP, increased renal medullary blood flow by 16+/-3% and 27+/-8%, respectively. The present experiments indicate that vasopressin V1 receptor stimulation serves to decrease renal medullary blood flow while V2 receptor stimulation appears to increase renal medullary blood flow; however, the net effect of AVP is to decrease renal medullary blood flow. 

Received 12 July 1994; accepted in final form 19 January 1995.
APS Manuscript Number R377-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.