Electrical Properties of Egg Cell Membranes

Abstract

The scope of this review is the electrical properties of the cell membrane. The first section concerns the resting potential, action potential, and K permeabilities of the cell membrane; these properties are compared with those of the maturing oocyte and early embryo. The second section concerns electrical phenomena associated with fertilization, in particular, the activation potential or fertilization potential and its function in prevent­ ing polyspermy and possibly in initiating development. Certain related topics have been reviewed elsewhere and are not discussed here: electrical phenomena associated with the establishment of pattern in the embryo (73); electrical coupling between blastomeres ( 124); and the development of membrane channels at later embryonic stages ( 139). Other reviews about the electrical properties of the cell membrane have been written (44, 58). One confusing issue in describing properties of eggs is the definitions of egg and oocyte. Two different definitions are commonly used. Some­ times the term oocyte is used to refer to stages not yet ready to be fertilized, whereas other authors distinguish oocytes and eggs according to the stage of meiosis, i.e. oocyte is used to refer to any stage before meiosis is complete and is used to refer to subsequent stages. This is confusing since in different species fertilization occurs at different stages of meiosis of the female gamete ( 13 1). (The male gamete has always completed meiosis at the time of fertilization.) Rather than attempt to reform this ambiguous usage, in general we have used the terminology used in the papers under discussion. 385