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Studies of phospholipase A 2 related to the hamster sperm acrosome reaction

1982; Wiley; Volume: 221; Issue: 1 Linguagem: Inglês

10.1002/jez.1402210114

1097-010X

Miguel Llanos, Chung W. Lui, Stanley Meizel,

Venomous Animal Envenomation and Studies

Abstract This report describes studies of innate and exogenous phospholipase A 2 related to the acrosome reaction of golden hamster cauda epididymal sperm in vitro. Two acrosome reaction‐inducing systems were used: a nonsyn‐chronous system with epinephrine, and a synchronous system with the protonionophore FCCP. After a high percentage of sperm had undergone AR (in both systems) an increased phosphatidylcholine hydrolyzing activity was found in incubation media supernatants after partial purification by Affi‐Gel Blue chromatography. A preliminary characterization demonstrates that the activity was stimulated by Ca 2+ , detectable at pH 7.4‐‐7.8, but not at pH 4.5, and inhibited by p‐bromophenacyl bromide and mepacrine. Thus, it appears that a phospholipase A 2 was released as a result of the acrosome reaction. BSA purified by TCA precipitation and ethanol resolubilization (TCA‐BSA), utilized in both types of incubations did not contain associated phospholipase A 2 activity, but did contain an associated phosphatidylcholine hydrolyzing activity. The nonphospholipase A 2 activity was removed by further purification of the TCA‐BSA by Affi‐Gel Blue chromatography, but the resulting highly purified TCA‐BSA was still able to induce capacitation and acrosome reactions in hamster sperm at the same level as prior to column chromatography. Incubations of the sperm in the presence of a partially purified bee venom phospholipase A 2 did not stimulate hamster sperm AR over control values in the presence of epinephrine, but did so in the absence of epinephrine (probably by mimicking the action of the innate sperm head phospholipase A 2 ). These results provide further support to earlier studies from this laboratory suggesting the involvement of a sperm head phospholipase A 2 as an important factor in the mammalian sperm acrosome reaction.