RESPONSE OF HUMAN SPERMATOZOA TO AN INTERNAL CALCIUM-ATPASE INHIBITOR, 2,5-DI(TERT-BUTYL) HYDROQUINONE

This study has investigated the effect of elevating intracellular calc ium levels, using an internal calcium ATPase inhibitor, 2,5-di(tert-bu tyl) hydroquinone (TBQ), on human sperm function. Isolated sperm sampl es from five fertile donors were incubated in a capacitating media for up to 6 hr. After 0, 3, and 6 hr incubation, sperm were exposed to a range of TBQ concentrations; 100 mu M, 10 mu M, and 1 mu M, for a fixe d incubation period of 5 min. Controls were run for each experiment wh ere sperm were incubated for 5 min in the absence of TBQ. Sperm capaci tation and the acrosome reaction were monitored prior to and after exp osure to TBQ, using the Chlortetracycline assay. In addition, sperm mo tility was assessed at each time point and after sperm had been expose d to TBQ. The treatment of sperm with TBQ caused a significant increas e in the number of capacitated sperm with an optimum response being ac hieved in the presence of 100 mu M TBQ. However, sperm motility was fo und not to be effected by the addition of TBQ. The results from the pr esent study suggest that elevating intracellular calcium levels in hum an sperm by short exposure to a high concentration of TBQ can rapidly accelerate the capacitation process. Furthermore, the observation that TBQ did not elicit a change in sperm motility suggests that TBQ may b e highly specific in its mode of action by acting within the head regi on of human sperm. (C) 1997 Wiley-Liss, Inc.