摘要：

Cellular secretion is a membrane fusion event of utmost importance. The Ca 2+ ion is critical in this process and its intracellular concentration is highly regulated. Therefore, Ca 2 + may play a direct or indirect role in these intracellular membrane fusion processes. One early indication of a direct role in membrane fusion was the observation that Ca 2 + could induce aggregation and leakage of contents from model membrane vesicles composed of the most abundant naturally occuring acidic phospholipid, phosphatidylserine (PS) ( Papahadjopoulos and Bangham, 1966 ) and that these phenomena were associated with fusion of the vesicles ( Papahadjopoulos et al., 1974 ). Subsequently, the ability to produce large unilamellar vesicles (LUV) ( Szoka and Papahadjopoulos, 1978 ; Szoka et al., 1980 ; Wilschut et al., 1980 ) and the development of fluorescent fusion assays ( Wilschut et al., 1980 ; Ellens et al., 1985 ) has allowed detailed studies of the factors that mediate Ca 2 +-dependent membrane fusion, particularly fusion of PS vesicles ( Wilschut et al., 1980 ). A simple mass action model for the kinetics of membrane fusion, that could describe or predict the results of fusion assays under certain conditions, resulted from such studies ( Nir et al., 1980a ; Bentz et al., 1983 ).

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