Cellular and Molecular Biology of Capacitation and Acrosome Reaction in Mammalian Spermatozoa

Abstract

Publisher Summary This chapter reviews the information available on different aspects of capacitation and acrosome reaction (AR) and proposes a tentative but unified view of the mechanisms involved in these phenomena. The capacitation is achieved in the female reproductive tract; it is also accomplished outside the female reproductive tract in numerous in vitro studies using well-defined media in several mammalian species. There is reasonable consensus that capacitation involves no morphological change in spermatozoa that can be discerned, even under the electron microscope; it does facilitate the occurrence of a distant morphological event in spermatozoa known as AR. AR involves point fusions between the outer acrosomal membrane and overlying plasmalemma leading to the release of acrosomal contents or enzymes required at the site of fertilization. The capacitation involves two important changes at the molecular level in spermatozoa: (1) sperm surface alteration and/or intramembranal molecular mobility to facilitate Ca 2+ influx and (2) changes in sperm energetics through alterations in oxygen uptake and glucose utilization manifested in the form of changes in pattern of flagellar beat.