EFFECT OF ATRIAL NATRIURETIC HORMONE ON HYPERTONIC SALINE-INDUCED SUPPRESSION OF THE RENIN-ALDOSTERONE SYSTEM

To evaluate the effect of physiologic doses of atrial natriuretic horm one (ANH) on hypertonic saline-induced renin-aldosterone system suppre ssion, nine healthy subjects were studied three times: 1) on a low-sal t (LS) diet with a 2 h placebo infusion; 2) on LS with 2 h infusion of human Ser-Tyr(28)ANH (0.6 pmol/kg/min)(LS + ANH); and 3) on a high-sa lt (HS) diet with a 2 h placebo infusion. On each study day during the second hour of infusion, subjects also received 3% saline (0.1 mL/kg/ min) infusion. Data from eight subjects were used for analysis because of a sampling error in one subject. During ANH infusion, plasma ANH l evels increased about twofold and reached levels similar to ANH levels on HS. Serum sodium increased by 3-4 mEq/L, and serum osmolality incr eased by 7-8 mOsm/L during 3% saline infusion on all study days. ANH l evels remained stable during 3% saline infusion. During the first hour of ANH infusion, plasma renin activity (PRA) decreased by about 24% a nd aldosterone levels by about 27%. Hypertonic saline caused further s uppression of PRA and aldosterone. The extent of the suppression was s imilar under each condition, and the levels at the end of hypertonic s aline infusion reached about 60% of the levels at the beginning of the saline infusion. We conclude that low-dose ANH infusion does not seem to have any major influence on PRA and aldosterone response to hypert onic saline.