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.
