ATRIAL-NATRIURETIC-PEPTIDE AND SODIUM HOMEOSTASIS IN COMPENSATED HEART-FAILURE

The purpose of this study was to determine whether high plasma levels of atrial natriuretic peptide (ANP) in compensated heart failure are i mportant in the maintenance of sodium balance. This was achieved by su bjecting eight dogs to bilateral atrial appendectomy (APX) to blunt th e ANP response to pacing-induced heart failure. Five intact dogs serve d as controls. In controls, 14 days of left ventricular pacing at 240 beats/min produced a sustained fall in cardiac output and mean arteria l pressure of similar to 40 and 20%, respectively; compared with cardi ac output, reductions in renal blood flow (up to similar to 25%) were less pronounced and even smaller decrements in GFR occurred (up to 9%) . Despite these changes and a threefold elevation in plasma norepineph rine concentration, plasma renin activity (PRA) did not increase and s odium balance was achieved during the second week of pacing in associa tion with a six- to eightfold rise in plasma levels of ANP. Similar re sponses occurred in four dogs in which APX was relatively ineffective in blunting the ANP response to pacing. In marked contrast, there were substantial increments in PRA and in plasma norepinephrine concentrat ion, and marked sodium and water retention during the last week of pac ing in four dogs with APX and severely deficient ANP. These results in dicate that ANP plays a critical role in promoting sodium excretion in the early stages of cardiac dysfunction.