Sex differences in vasopressin V2 receptor expression and vasopressin-induced antidiuresis

The renal vasopressin V2 receptor (V2R) plays a critical role in physiological and pathophysiological processes associated with arginine vasopressin (AVP)-induced antidiuresis. Because clinical data suggests that females may be more prone to hyponatremia from AVP-mediated antidiuresis, we investigated whether there are sex differences in the expression and function of the renal V2R. In normal Sprague-Dawley rat kidneys, V2R mRNA and protein expression was 2.6- and 1.7-fold higher, respectively, in females compared with males. To investigate the potential physiological implications of this sex difference, we studied changes in urine osmolality induced by the AVP V2R agonist desmopressin. In response to different doses of desmopressin, there was a graded increase in urine osmolality and decrease in urine volume during a 24-h infusion. Females showed greater mean increases in urine osmolality and greater mean decreases in urine volume at 0.5 and 5.0 ng/h infusion rates. We also studied renal escape from antidiuresis produced by water loading in rats infused with desmopressin (5.0 ng/h). After 5 days of water loading, urine osmolality of both female and male rats escaped to the same degree physiologically, but V2R mRNA and protein in female kidneys was reduced to a greater degree (−63% and −73%, respectively) than in males (−32% and −48%, respectively). By the end of the 5-day escape period, renal V2R mRNA and protein expression were reduced to the same relative levels in males and females, thereby abolishing the sex differences in V2R expression seen in the basal state. Our results demonstrate that female rats express significantly more V2R mRNA and protein in kidneys than males, and that this results physiologically in a greater sensitivity to V2R agonist administration. The potential pathophysiological implications of these results are that females may be more susceptible to the development of dilutional hyponatremia because of a greater sensitivity to endogenously secreted AVP