Participation of oviducal pars recta secretions in inducing the acrosome reaction and release of vitelline coat lysin in fertilizing toad sperm

[摘要] Jellylesscoelomiceggsofthetoad,Bufobufojaponicus,arenotfertilizablewheninseminatedinjellycomponentsthatassurefertilizationofdejellieduterineeggs.However,whencoelomiceggswerepretreatedwithanextractfromtheuppermostportionofoviduct(parsrecta)andinseminatedinjelly,ahighfrequencyoffertilizationwasobtained.Thisactivitywasobservedonlyintheparsrectaextract(PRE)preparedfrompituitary-injected,ovulatingfemales.TreatmentofcoelomiceggswiththePREfollowedbyadditionofspermwithoutjellyresultedinlysisofthevitellinecoat(VC).Likewise,thesupernatantofthePREpreincubatedwithspermhadastrongVClyticactivity.TheTritonX-100extractofspermpreincubatedwiththePREexhibitedlessthan20%oftheproteolyticactivityinextractsofcontrol,untreatedsperm.ElectronmicroscopyofspermrevealedthatthePREtreatmentinducesaspecificlossoftheacrosomalcap.Electronmicroscopically,distinctfilamentbundlesoftheVCincoelomiceggsbecamelessconspicuous,aftereggspassedthroughtheparsrectaorweretreatedwiththePRE.Epithelialcellsintheparsrectacontaineduniquenonciliatedcellsthatpossesselectron-densegranulesdistinctfromthoseinjelly-secretingcellsinloweroviducalportions.Thenumberofthesegranulesineachcellincreasedsignificantlyuponinjectionofpituitaryhormoneintofemales.Immunohistochemicalobservationsprovedthatthespecificantigen(s)localizedinnonciliatedcellsintheparsrectaisnotdetectedintheVCofcoelomiceggs,butisdepositedintheVCduringpassageofeggsthroughtheparsrecta.Itisconcludedthatthesubstance(s)secretedfromtheparsrectacellsisdepositedintheVC,andinducestheacrosomereactionandreleaseofVClysininspermtoensurethattheymakeasuccessfulfusionwiththeeggplasmamembrane.

[学科分类] 生物科学（综合）