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 50% effective concentration calculated on the total added ATPe are 0.1 and 2 mM, respectively, corresponding to a free ATP concentration (ATP4-) of 3 and 200 microM, respectively. The ATPe-gated channel is selective for monovalent cations (Na+, choline, and methylglucamine), whereas on the contrary, permeability to Ca2+ is negligible. Isosmolar 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 that might have an important role in sperm activation before egg fertilization.
mechanism of human sperm activation by extracellular atp
DI VIRGILIO, Francesco
1996
Abstract
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 50% effective concentration calculated on the total added ATPe are 0.1 and 2 mM, respectively, corresponding to a free ATP concentration (ATP4-) of 3 and 200 microM, respectively. The ATPe-gated channel is selective for monovalent cations (Na+, choline, and methylglucamine), whereas on the contrary, permeability to Ca2+ is negligible. Isosmolar 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 that might have an important role in sperm activation before egg fertilization.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
