Mechanism of human sperm activation by extracellular atp.
Foresta, Carlo, Marco Rossato, Paola Chiozzi & Francesco Di
Virgilio.
Universit[grave]a di Padova, III Cattedra di Patologia Medica, Via
Ospedale Civile 105, I-35121 Padova, Italia, and Universit[grave]a di
Ferrara, Istituto di Patologia Generale, Via Borsari 46, I-44100
Ferrara, Italia
APStracts 2:0454C, 1995.
We have identified the mechanism whereby extracellular ATP (ATPe)
triggers the acrosome reaction in human spermatozoa. This nucleotide
opens a ligand-gated ion channel expressed on the sperm plasma
membrane. ATPe threshold and EC50 calculated on the total added ATPe
are 0.1 and 2 mM, respectively, corresponding to a free ATP
concentration (ATP4-) of 3 and 200 uM, respectively. The ATPe-gated
channel is selective for monovalent cations (Na+, choline and
methylglucamine) while on the contrary permeability to Ca2+ is
negligible. Iso-osmolar replacement of extracellular Na+ with sucrose
fully blocked ATPe-dependent sperm activation, thus suggesting a
mandatory role for Na+ influx. These results show that human sperm
express an ATPe-gated Na+ channel which might have an important role
in sperm activation before egg fertilization.
Received 19 January 1995; accepted in final form 7 December 1995.
APS Manuscript Number C38-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95