RENAL TUBULAR SODIUM HANDLING AND PLASMA ATRIAL-NATRIURETIC-PEPTIDE, RENIN-ACTIVITY AND ALDOSTERONE IN UNTREATED MEN UNDER NORMAL LIVING-CONDITIONS

The associations between renal tubular sodium handling and plasma levels of atrial natriuretic peptide, renin activity and aldosterone were studied in 295 untreated men under normal living conditions. The renal clearance of ingested lithium was used as a marker of proximal tubular sodium handling. Plasma atrial natriuretic peptide was inversely related to creatinine clearance (r = -0.148, P < 0.01) and directly and significantly related to the overall fractional excretion of sodium (r = 0.213, P < 0.001) and to distal (r = 0.151, P < 0.01) fractional sodium excretion. Plasma renin activity was inversely related to sodium excretion at both proximal (r = -0.145, P < 0.05) and distal (r = -0.236, P < 0.001) tubular site, whereas plasma aldosterone was significantly and inversely related to distal sodium excretion only (r = -0.305, P < 0.001). The association between plasma atrial natriuretic peptide and distal sodium excretion in a large sample of men under normal living conditions supports the view of a possible tubular effect of the hormone for the overall control of sodium excretion in man.