Effect of intrarenal bradykinin infusion on vasopressin release in rabbits.

Electrical stimulation of afferent renal nerves and activation of renal mechanoreceptors increase plasma vasopressin concentrations. In the present study, the effect of renal chemoreceptor activation on plasma vasopressin concentration was investigated in anesthetized rabbits. Renal chemoreceptors were activated with intrarenal infusions of bradykinin. With intrarenal infusion of bradykinin at 136 ng/min, plasma vasopressin concentration increased from 4.5 +/- 1.5 to 26.8 +/- 14.2 pg/ml at 5 minutes (p less than 0.01), whereas with infusion at 1,360 ng/min, plasma vasopressin increased from 5.9 +/- 2.0 to 54.4 +/- 16.4 pg/ml at 5 minutes (p less than 0.01). There was no significant change in plasma vasopressin during intravenous infusion of bradykinin at 136 ng/min. Infusion at 1,360 ng/min increased plasma vasopressin from 2.7 +/- 0.5 to 14.8 +/- 6.4 pg/ml (p less than 0.01), but this increase was significantly less than that produced by intrarenal infusion of the same dose of bradykinin. Similar effects on plasma vasopressin were observed during paired intrarenal and intravenous infusions of bradykinin at 136 ng/min. Renal denervation markedly reduced the vasopressin responses to intrarenal infusion of bradykinin at 136 ng/min (2.8 +/- 0.5 to 4.0 +/- 0.7 pg/ml, p less than 0.01) and 1,360 ng/min (3.2 +/- 0.7 to 7.8 +/- 1.8 pg/ml, p less than 0.05). These results indicate that bradykinin stimulates vasopressin release by an intrarenal action and suggest that this action is mediated by afferent renal nerves.