LOCALIZATION OF THE VASOPRESSIN V-1A AND V-2 RECEPTORS WITHIN THE RENAL CORTICAL AND MEDULLARY CIRCULATION

Localization of the vasopressin V-1a and V-2 receptors within the rena l cortical and medullary circulation. Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol. 42): R243-R251, 1997.-Arginine vasopressin (AVP) is a potent vasoconstrictor that preferentially reduces renal me dullary blood flow through the stimulation of the vasopressin V-1a rec eptor (V1aR). Studies have also shown that the vasopressin V-2 recepto r (V2R) may modulate AVP-mediated vasoconstriction. At present, the di stribution of the V1aR and V2R within the renal cortical and medullary microcirculation has not been determined. This study was designed to localize the transcriptional and translational sites of the V1aR and V 2R in microdissected intrarenal vascular segments from both the cortex and medulla, specifically the interlobar, arcuate, and interlobular a rteries; afferent and efferent arterioles; glomeruli; and single outer medullary vasa recta capillaries using reverse transcription-polymera se chain reaction and Western blot analyses. The results indicated tha t V1aR mRNA and proteins were present in the isolated cortical or medu llary vasculature, but the V2R mRNA and proteins were not found. This study suggests that the vasoconstrictor action of AVP within the renal medulla is mediated through the V1aR and that the modulatory V2R-medi ated vasodilation is probably through the release of paracrine hormone s found within the renal interstitial or tubular cells.