Renal response to AVP and DDAVP after angiotensin II blockade in the rat

Inhibition of the renin-angiotensin system with saralasin or with SQ 20,881 was used to examine a possible interaction between endogenous angiotensin II and antidiuretic hormone in renal water excretion. In sodium-depleted anesthetized rats undergoing water diuresis, neither saralasin nor SQ 20,881 had any significant effect on water excretion. Both drugs, however, markedly potentiated the antidiuretic response to arginine vasopressin. A similarly enhanced antidiuresis was also observed when the renal response to 1-desamino-8-D-arginine vasopressin was investigated in the presence or absence of saralasin. There were no significant changes in sodium or potassium excretion or in glomerular filtration rate in any of the groups studied. Neither was there any interaction of the drugs with relation to blood pressure. These results seem to indicate that endogenous angiotensin II is capable of antagonizing the hydroosmotic effect of antidiuretic hormone.