Atrial natriuretic peptide attracts human spermatozoa in vitro

Here we report that atrial natriuretic peptide (ANP), a known activator of particulate guanylate cyclase, induces attraction and swimming speed enhancement of human spermatozoa in vitro. Using capillary assays under a variety of experimental conditions (ascending or descending gradients of ANP, or no gradient at all) and microscopic assays in which individual spermatozoa could be followed, we found that spermatozoa followed the gradient of ANP and accumulated in it. Speed enhancement was detected in the presence of ANP without a gradient. These observations suggest either that an ANP-like substance is the physiological attractant for human spermatozoa, or, more likely, that ANP directly affects guanylate cyclase in a manner similar to that caused by the physiological attractant.