정자의 수정능력획득과 첨체반응은 Ca에 의존적으로 일어나며, 수정능력획득 과정에서는 원형질막으로부터 cholesterol이 방출되어 첨체반응이 일어나기 쉬운 상태로 전환된다. 최근 세포막으로부터 cholesterol 방출을 촉진하는 methyl beta cyclodextrin (MBCD)이 첨체반응을 유발함이 알려졌으나 정자 주변의 Ca 농도와 관계없이 cholesterol 방출만으로 첨체반응이 유발되는지의 여부는 확인되지 않았다. 본 연구에서는 생쥐

Sperm capacitation and acrosome reaction (AR) have been known to be Ca-dependent events. Sperm capacitation accompanies with cholesterol efflux fiom plasma membrane, that eventually stimulates AR. However, whether the AR mediated by cholesterol efflux is Ca dependent has not been verified yet. Recently, methyl beta cyclodextrin (MBCD) was found to evoke AR by stimulating the cholesterol efflux fiom sperm membrane. In the present study, we examined the requirement of Ca in the MBCD-induced AR. During incubation of sperm in the bicarbonate buffered media MBCD increased AR in a dose-dependent manner regardless of the Ca presence. In the presence of low molar concentration of Ca (100 M), MBCD-induced AR was slightly increased compared to Ca-free condition. In the absence of Ca supplement, spontaneous AR was slightly increased during the incubation but inhibited by 100 M EGTA. MBCD potentiated AR even the presence of EGTA. However, EGTA attenuated MBCD-induced AR, suagesting the functional involvement of intracellular Ca in the MBCD-induced AR. Taken together, it was suggested that cholesterol efflux from the sperm plasma membrane was sufficient for induction of AR even in the absence of extracellular Caand that a condition permissive for mobilization of intracellular Ca is important for MBCD-induced AR.

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