AJP - Cell Physiology, Vol 262, Issue 5 C1095-C1101, Copyright © 1992 by American Physiological Society
Precontact mammalian sperm-egg communication and role in fertilization
M. Eisenbach and D. Ralt
Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.
In creatures with external fertilization, e.g., metazoa, it is well
established that there is precontact sperm-egg communication in the form of
chemotaxis. An intriguing question is whether also in mammals, where
fertilization is internal and the need for precontact sperm-egg
communication is not self-evident, such a process occurs and what its
physiological significance may be. Here we review the evidence related to
such a process in mammals, evidence which suggests that sperm attraction to
the ovulated egg may indeed occur. On the basis of the available data we
propose a hypothesis, according to which a sperm population is
heterogeneous with respect to its physiological state; some spermatozoa are
at a physiological state ready for fertilizing an egg, while others are
premature or overmature. According to the hypothesis this is a dynamic
state; the population of fertilizing spermatozoa gradually loses its
potency and, at the same time, other spermatozoa mature and acquire
fertilizing ability. After ovulation, only the fertilizing spermatozoa are
attracted to the egg, while the rest are either repelled or inhibited and
thus prevented from reaching the egg. The potential significance of
sperm-egg communication is discussed.
