title: Intracellular calcium responses in bovine oocytes induced by spermatozoa and by reagents.
abstract: The objectives of the present study were to clarify and compare the characteristics of the transient rises in intracellular calcium concentrations ([Ca2+]i) induced either by spermatozoa or by stimulation with artificial activators in bovine oocytes. These transient rises in [Ca2+]i in oocytes matured in vitro were recorded with Ca2+ imaging using the Ca2+ indicator fura-2. During fertilization, a series of transient rises in [Ca2+]i was observed. The first Ca2+ response peaked at a concentration of 521 +/- 39 nM (n = 20) and lasted for 4 min, while the subsequent Ca2+ responses were significantly smaller and shorter, with a peak of 368 +/- 13 nM (n = 23) and a duration of 2 min. Injection of inositol 1,4,5- triphosphate (InsP3) into unfertilized oocytes caused a transient rise in [Ca2+]i in a dose-dependent manner. The maximum response was induced by 20 nA x 1 sec injection of InsP3. Thimerosal, a sulfhydryl reagent, induced the repetitive transient rises in [Ca2+]i. The peak and the duration of the rises in [Ca2+]i induced by InsP3 or thimerosal were smaller and shorter, respectively, than those of the first rise induced by spermatozoa. Ethanol and Ca2+ ionophore IA23187, which are general parthenogenetic activators of unfertilized oocytes, each induced a single transient rise in [Ca2+]i. The duration of the rise in [Ca2+]i by ethanol or Ca2+ ionophore was significantly longer than that by spermatozoa at fertilization, although the peaks were smaller. These results clarified the characteristics of the rises in [Ca2+]i induced by spermatozoa and by several artificial reagents, and showed that the first rise in [Ca2+]i induced by spermatozoa had a higher peak [Ca2+]i and a longer duration compared with each the subsequent rises in [Ca2+]i and the rises in [Ca2+]i induced by artificial reagents. These indicate that a mode like as the first rise in [Ca2+]i induced by spermatozoa is an effective trigger for artificial activation of oocytes.
authors.affiliation: Department of Veterinary Obstetrics and Gynecology, Rakuno Gakuen University, Hokkaido, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakada
authors.forename: J
authors.initials: J
authors.lastname: Mizuno
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002417:Cattle / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D007202:Indicators and Reagents / Q000494:pharmacology*; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D010312:Parthenogenesis; D013084:Sperm-Ovum Interactions; D013849:Thimerosal / Q000494:pharmacology
chemical_list: D007202:Indicators and Reagents; D007476:Ionophores; D013849:Thimerosal; D000001:Calcimycin; D000431:Ethanol; D002118:Calcium