Effects of relaxin on the fertilization capacity of human spermatozoa.

Relaxin, a polypeptide hormone found in human seminal plasma, exerted favorable effects on the function of spermatozoa. This study was designed to investigate the effect of this hormone on the fertilization capacity of human spermatozoa from 10 oligospermic men (group A), 11 asthenospermic men (group B), 10 normospermic infertile men (group C), and 10 men with verified fertility (group D). We compared the effects of purified porcine relaxin at different concentrations (0, 50, and 150 ng/ml). Parameters include motility, hypoosmolar swelling test, and zona-free hamster egg penetration test. In group A and group B, relaxin increased the results of the hamster egg penetration test and motility. In group C, results of the hamster egg penetration test and motility improved only at the concentration of 50 ng/ml. In group D, relaxin increased the results of the hamster egg penetration test only at a concentration of 150 ng/ml. Results of the hypoosmolar swelling test were not consistently altered in any study group. Relaxin appears to enhance the fertilization capacity and motility of human spermatozoa in oligospermic and asthenospermic subjects.