CIRCADIAN RELATIONSHIPS BETWEEN CIRCULATING ATRIAL NATRIURETIC PEPTIDES AND SERUM-CALCIUM AND PHOSPHATE IN HEALTHY HUMANS

Long-acting natriuretic peptide (LANP), vessel dilator (VSDL), and atr ial natriuretic factor (ANF) consisting of amino acids (aa) 1 to 30, 3 1 to 67, and 99 to 126, respectively, of the 126-aa ANF prohormone cir culate in humans. Among the biologic properties of these peptides is t he ability of ANF to decrease intracellular calcium concentrations. To determine if atrial natriuretic peptides are directly related to seru m calcium and/or phosphate in healthy normocalcemic humans, we examine d 21 24-hour profiles of VSDL, LANP, ANF, and serum calcium and phosph ate in 14 healthy humans. VSDL, LANP, and ANF each had significant (P < .001) circadian rhythms, with peak concentrations late during sleep (at 4:00 AM) being nearly twice the concentrations in the afternoon an d evening. Serum calcium and phosphate also had significant circadian rhythms (P < .001) with troughs nearly opposite to those of the atrial natriuretic peptides, suggesting that atrial peptides may be importan t in the modulation of the circadian rhythms of calcium and phosphate. The nearly identical circadian rhythms of the atrial natriuretic pept ides and of parathyroid hormone (PTH) reported by others, along with e vidence that PTH may increase atrial peptide release, suggest that som e of the effects attributed to PTH may be mediated by atrial natriuret ic peptides. Copyright (C) 1996 by W.B. Saunders Company