Cytochalasin B: Its morphological and electrophysiological actions on synthetic strands of cardiac muscle☆

[摘要] SyntheticstrandsofcardiacmusclegrownintissueculturefromembryonicchickheartcellswereexposedtocytochalasinB(10–40μg/ml)foraslongas4hr.Duringthistime,intracellularmicroelectrodeswereusedtostudytheelectricalpropertiesofthestrands,andcontractileactivitywasmonitoredbymeansofaclosedciruittelevision-microscopysystem.Theareasofthestrandsfromwhichrecordingswereobtainedwereexaminedbylightandelectronmicroscopy.Inthepresenceofcytochalasintheactionpotentialdecreasedinamplitude,overshoot,andmaximumrateofdepolarization(V̇max),concomitantwithanincreaseinduration.TheS-shapedrelationshipbetweenV̇maxandmembranepotentialshiftedtotheright(themaximumvalueswerereducedbyafactorof2),andtheconductionvelocitydecreasedby30%.Contractilityceasedonlywhenthepreparationbecameelectricallyinexicitable.TheelectrophysiologicaldatasuggestthatcytochalasinreducesthenumberofNa-carryingchannelsperunitareaofmembraneaswellastheeffectivenumberoffibersperunitcross-sectionalareaofthepreparation.Correlativemicroscopicstudiesoftreatedpreparationsshowedthatcytochalasindisaggregatesthefiberintoindividualcellsbydisruptingcelljunctionsandinsomeregions,disruptsmyofibrils.Cytochalasinisthusshowntobeamembrane-activedrugthatalsodisruptstheintegrityofcardiacmuscleonthetissueandcelllevel.

[学科分类] 生物科学（综合）