RENAL HYPERSENSITIVITY TO VASOPRESSIN IN CONGESTIVE-HEART-FAILURE

Plasma vasopressin (AVP) levels are often elevated in congestive heart failure (CHF). To determine the significance of AVP in CHF, we perfor med clearance studies on the UM-X7.1 strain of cardiomyopathic (CM) ha msters with moderate heart failure and age-matched healthy controls. E xogenous AVP or a selective V-2 agonist (0.3 ng.kg(-1).min(-1)) reduce d the fractional excretion of sodium (FENa) and water (FEH2O) by 40-46 % in the control group. Although the CM hamsters exhibited a blunted p hysiological response to the V-2 agonist, their urinary cAMP levels we re fivefold that of normal and reflect an altered regulation of V-2 re ceptor signalling during CHF. Additional studies also showed that infu sion of a V2 antagonist (0.3 ng.kg(-1).min(-1)) produced natriuresis a nd diuresis in CM hamsters (FENa: 7.9 +/- 1.1 vs. 4.8 +/- 0.6%, p < 0. 05; FEH2O: 2.2 +/- 3 vs. 1.5 +/- 0.2%, p < 0.05) but did not decrease fluid reabsorption in the normal hamsters. In conclusion, the attenuat ed renal response to exogenous AVP in CM hamsters may be attributed to an enhanced endogenous AVP response during CHF.