ATRIAL-NATRIURETIC-PEPTIDE - A CHEMOATTRACTANT OF HUMAN SPERMATOZOA BY A GUANYLATE CYCLASE-DEPENDENT PATHWAY

Atrial natriuretic peptide (ANP), found in mammalian ovarian granulosa cells and oocytes (Kim et al., 1992, 1993), induces the human acrosom e reaction (Anderson et al., 1994). The purpose of the present study w as to determine whether ANP, as egg-derived peptides from sea urchins, can act as a chemoattractant to human spermatozoa. Small lengths of c apillary tubing that contained different concentrations of ANP were su spended over a suspension of washed spermatozoa. The number of spermat ozoa that entered the tubing was determined. More than twice the numbe r of spermatozoa moved into the tubing that contained a maximally effe ctive concentration of ANP, as compared with tubing that contained onl y medium. The concentration of ANP that produced a half-maximal effect was 0.7 nM. The effect was blocked by LY83583, an inhibitor of guanyl ate cyclase. ANP produced more than a twofold increase in the rate of cGMP formation, an effect that was blocked by LY83583. Human ANP (5-27 ), a fragment of the intact peptide, had no chemoattractant activity. These findings suggest that a specific sperm receptor exists for the c hemoattractant activity of ANP that is associated with guanylate cycla se. The chemoattractant activity of ANP is independent of the presence of extracellular calcium ions and is independent of the action of ANP as a stimulus of the acrosome reaction. There is no association betwe en the chemoattractant activity of follicular fluid and the follicular fluid concentration of ANP. These data suggest that factors besides A NP are responsible for the chemoattractant activity of follicular flui d. The present study adds to evidence that human ANP is a potent modul ator of human sperm function. (C) 1995 Wiley-Liss, Inc.