Changes in sperm phosphotyrosine proteins by human follicular fluid in mice

The effects of follicular fluid on the acrosome reaction (AR) and phosphorylation of tyrosine residues of the sperm proteins were examined in mouse epididymal sperm. Human follicular fluid (hFF) increased AR in the capacitated sperm. Genistein, a receptor tyrosine kinase (RTK) inhibitor, inhibited spontaneous AR. When the genistein was primed, hFF-induced AR was attenuated but the A23187-induced AR was not, suggesting that potentiation of AR by hFF attributed to the activation of RTK upstream the mobilization of Ca2+. Phosphotyrosine proteins of Mr 27 to 116 kDa were markedly increased in capacitated sperm but this increase was abrogated by genistein. hFF increased tyrosine phosphorylation of Mr 56 kDa protein with genistein sensitive manner, suggesting that 56 kDa phosphotyrosine protein might be involved in capacitation and AR by follicular fluid.