The In vitro Effect of Exogenous Melatonin on Motility of Human Spermatozoa

Abstract

Melatonin, a hormone secreted by the pineal gland is preesnt in the semen and melatonin binding sites have been demonstrated on the plasma membrane of sperm. These observations suggest a possible modulatory role of melatonin on sperm function. The aim of this study was to investigate the effects of melatonin on motility of human sperm in vitro. The concentration tested were 75, 150, 300, 450 and 900 pg mL-1 and the period of investigation was 120 min. The results show that, at all concentrations tested, melatonin suppressed motility of sperm. This antimotility effect was not dose-dependent but was time-dependent ; the greatest inhibition for a particular concentration being evident at the highest time point of incubation. Melatonin was not necrospermic but was only spermiostatic. Furthermore, it did not markedly alter the functional integrity of sperm of plasma membrane as revealed from the hypoosmotic swelling test. It is suggested that the sperm antimotility effect of melatonin may be due to its membrane stabilizing actions.