Antihypertensive effect of transplant of rat kidney or its unclipping. Hemodynamic effects and control mechanisms.

The acute transplantation of a normal kidney into a recipient rat with Goldblatt one-kidney, one clip hypertension (1K1C) results in a blood pressure (BP) fall toward but not below normal levels within 1 hour. Removal of the clip in a 1K1C hypertensive rat also normalizes the BP rapidly. These changes are not mediated by external fluid loss and occur after indomethacin pretreatment, but are associated with a fall in cardiac output. The mechanism of release of a depressor secretion from the kidney transplant appears to be under barostatic control. Thus, transplanting a kidney into a hypertensive recipient caused a prompt BP decline, whereas transplanting an SHR kidney into a hypertensive recipient did not lower the BP. The prompt BP fall seen after unclipping also indicates that abrupt exposure of the kidney to a high perfusion pressure initiates the release of some depressor agent. When the recipient rat was made hypertensive by injecting renin, the kidney transplant did not lower the BP. When angiotensin in subpressor dose was infused into the renal artery of the kidney transplant, the BP of the recipient did not fall, whereas infusion of norepinephrine in equiconstrictor doses did not prevent the depressor response. These experiments suggest that, in addition to a barostatic stimulus for depressor release, angiotensin acts as a specific inhibitor.