The ascidian sperm reaction: Ca2+ uptake in relation to H+ efflux☆
[摘要] Duringtheascidianspermreactionthesinglelargecylindricalmitochondrionwhichliesnexttothenucleusintheheadswells,becomesspherical,andmigratesalongthetailtobelostwhenitreachestheend.Thissequenceisinitiatedbyeggs,eggwater,highpH,lowNa+,ortheionophoreX537A.AccompanyingthespermreactioninducedbylowNa+areH+effluxandCa2+influxinaratioofnear100:1asdeterminedby45Ca2+andatomicabsorptionanalysis.SimultaneouspHandCa2+electrodemeasurementssuggestthatthemovementofH+begins10–13secbeforethemovementofCa2+.Ca2+uptakecanbeinhibitedbyverapamilwithoutaffectingH+effluxorthespermreaction.AcidreleaseandCa2+uptakeareproportionaltotheinitialpHofthemediumwhenthereactionistriggeredbyhighpH.AcidreleaseinitiatedbylowNa+isproportionaltoCa2+concentrationsabove2mM.H+andCa2+movementsdifferinmagnitude,kinetics,andinhibitionbyverapamil,thussuggestingthatH+isprobablynotexchangedforCa2+.InsteadweproposethatlossofH+triggerstheuptakeofCa2+,whichinitiatesthespermreaction.
[发布日期] [发布机构]
[效力级别] [学科分类] 生物科学（综合）
[关键词] [时效性]
