Lack of effect of exogenous relaxin on the fertilizing capacity of human spermatozoa

Abstract

The presence of immunoreactive relaxin in human seminal plasma has recently been documented. The potential function for seminal plasma relaxin in spermatozoal physiology was investigated by studying the effect of exogenous relaxin on the in vitro penetration of zona-free hamster ova by human spermatozoa. Biggers, Whitten and Whittingham (BWW) medium-washed spermatozoa from 12 fertile men were incubated with different concentrations (0, 10, 50, 100 and 200 ng/ml) of purified porcine relaxin (NIH-RXN-P1) in BWW at 37° for 5 hours. After incubation, the spermatozoa suspensions were centrifuged, the supernatant discarded, and the pellets resuspended in BWW before insemination of the denuded hamster ova. The penetration rates were scored 6 hours later. Results between the control and the relaxin-treated groups were analyzed statistically. The penetration rate for the non-treated spermatozoa from fertile men was 21%, which was not significantly different (p > 0.05) from the penetration rates observed with the relaxin-treated spermatozoa (10 ng/ml, 24%; 50 ng/ml 27%; 100 ng/ml, 20%; 200 ng/ml, 25%). These findings indicate that exogenous relaxin does not affect the human spermatozoal fertilizing capacity in vitro. The role of seminal plasma relaxin in the human spermatozoal capacitation and fertilization process merits further investigation.