Localization of the vasopressin V(1a) and V₂ receptors within the renal cortical and medullary circulation

Arginine vasopressin (AVP) is a potent vasoconstrictor that preferentially reduces renal medullary blood flow through the stimulation of the vasopressin V(1a) receptor (V(1a)R). Studies have also shown that the vasopressin V₂ receptor (V₂R) may modulate AVP-mediated vasoconstriction. At present, the distribution of the V(1a)R 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 V(1a)R and V₂R in microdissected intrarenal vascular segments from both the cortex and medulla, specifically the interlobar, arcuate, and interlobular arteries; afferent and efferent arterioles; glomeruli; and single outer medullary vase recta capillaries using reverse transcription-polymerase chain reaction and Western blot analyses. The results indicated that V(1a)R mRNA and proteins were present in the isolated cortical or medullary 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 V(1a)R and that the modulatory V₂R-mediated vasodilation is probably through the release of paracrine hormones found within the renal interstitial or tubular cells.