Calcium influx following fertilization of Urechis caupo eggs☆

[摘要] Measurementsof45CafluxintoandoutofUrechiseggsindicatethat,duringthefirst10minafterinsemination,theeggstakeup0.24pmoleofCa/egg.TotaleggCameasuredbyatomicabsorption(AA)spectroscopyincreasedby0.23pmoleofCa/egg(0.56,0.79,and0.76pmoleofCa/eggforunfertilized,10-minfertilized,and60-minfertilizedeggs,respectively).Thus,thetotalchangeineggCaisaccountedforbytheinfluxeventhoughtherateofefflux,measuredasareleaseof45Cafrompreloadedeggs,increasestotwicetheunfertilizedrateby15min.Thefertilizationinfluxfollowssaturationkinetics(Ka=1.3mM).Itiscompetitivelyinhibitedbyprocaine,butisnotinhibitedbydinitrophenol,mersalylacid,orrutheniumred.TenpercentofthetotalCainfluxhasoccurredby10sec,anditis,therefore,themostrapidresponsetofertilizationyetknownintheseeggs.TheinfluxisalsoobservedineggspartiallyactivatedbyinseminationinpH7seawater(SW);theotherfertilizationresponses,exceptspermpenetration,donotoccurinpH7SW.AlthoughCainfluxaloneisinsufficienttoactivatetheeggs,itmaybeaprerequisiteforcytoplasmicactivationanddevelopment,inducingothersecondaryresponseswhicharepreventedbylowexternalpH.

[学科分类] 生物科学（综合）