The participation of eicosanoids in the acrosome reaction, the crucial step of fertilization, has been investigated in various animal species and in humans. The term 'acrosome reaction' describes the process of penetration of a spermatozoon into the glycoprotein-containing zona pellucida of the egg preceding the fusion of both gametes. During this process the acrosome at the head of the spermatozoon releases proteolytic enzymes, for example hyaluronidase, thus dissolving the glycoprotein coat and locally producing a channel through which the spermatozoon can enter the egg. The acrosome reaction is initiated by zona pellucida components, which probably trigger calcium entry into the spermatozoa. The subsequent intracellular mechanism by which fusogenic mediators are activated has not yet been unequivocally elaborated. It has been demonstrated by several investigators that arachidonic acid and certain prostaglandins (for example PGE2) are able to induce the acrosome reaction and that phospholipases A2, C and D as well as protein kinase C play important roles . However, the exact role of eicosanoids in this process remains controversial [218,219].
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