Effect of relaxin on human spermatozoa.

To study its effect on the motility of human spermatozoa, relaxin was added at different concentrations to human semen samples of various qualities as well as to washed spermatozoa. Relaxin in physiologic concentrations (10-100 ng/mL) had no significant effect on sperm motility in normal semen samples. However, the addition of relaxin to semen samples with low sperm motility significantly increased the motility. Addition of relaxin similarly increased the motility of spermatozoa from normal semen samples that were either aged or washed; the treatment resulted in a decrease in motility. When sperm motility was optimal, as in normal samples, addition of relaxin did not increase motility. However, in some situations of decreased motility, addition of relaxin resulted in improvement of spermatozoan motility. Relaxin may have clinical value in the treatment of male infertility.