title: Ca2+ ionophore A23187 can make mouse spermatozoa capable of fertilizing in vitro without activation of cAMP-dependent phosphorylation pathways.
abstract: Ca(2+) ionophore A23187 is known to induce the acrosome reaction of mammalian spermatozoa, but it also quickly immobilizes them. Although mouse spermatozoa were immobilized by this ionophore, they initiated vigorous motility (hyperactivation) soon after this reagent was washed away by centrifugation. About half of live spermatozoa were acrosome-reacted at the end of 10 min of ionophore treatment; fertilization of cumulus-intact oocytes began as soon as spermatozoa recovered their motility and before the increase in protein tyrosine phosphorylation, which started 30-45 min after washing out the ionophore. When spermatozoa were treated with A23187, more than 95% of oocytes were fertilized in the constant presence of the protein kinase A inhibitor, H89. Ionophore-treated spermatozoa also fertilized 80% of oocytes, even in the absence of HCO3(-), a component essential for cAMP synthesis under normal in vitro conditions. Under these conditions, fertilized oocytes developed into normal offspring. These data indicate that mouse spermatozoa treated with ionophore are able to fertilize without activation of the cAMP/PKA signaling pathway. Furthermore, they suggest that the cAMP/PKA pathway is upstream of an intracellular Ca(2+) increase required for the acrosome reaction and hyperactivation of spermatozoa under normal in vitro conditions.
authors.affiliation: Department of Biological Sciences, Asahikawa Medical University, Asahikawa, Hokkaido 078-8510, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tateno
authors.forename: Dario
authors.initials: D
authors.lastname: Krapf
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hino
authors.forename: Claudia
authors.initials: C
authors.lastname: Sánchez-Cárdenas
authors.forename: Alberto
authors.initials: A
authors.lastname: Darszon
authors.forename: Ryuzo
authors.initials: R
authors.lastname: Yanagimachi
authors.forename: Pablo E
authors.initials: PE
authors.lastname: Visconti
mesh_terms: D000818:Animals; D015153:Blotting, Western; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D005306:Fertilization / Q000187:drug effects*; D008297:Male; D051379:Mice; D010766:Phosphorylation; D011247:Pregnancy; D011256:Pregnancy Outcome; D015398:Signal Transduction / Q000502:physiology; D013075:Sperm Capacitation / Q000187:drug effects*; D013094:Spermatozoa / Q000187:drug effects* / Q000502:physiology
chemical_list: D000001:Calcimycin; D000242:Cyclic AMP; D002118:Calcium
keywords: calcium; sperm capacitation