Changes in sensitivity to anoxia of the cardiac action potential plateau during chick embryonic development

[摘要] Theeffectsofanoxiaoncardiacactionpotentialswerestudiedatdifferentstagesofdevelopmentofembryonicchickheart.Theplateauphaseoftheactionpotentialwasmarkedlydepressedbyanoxiainold(15–16daysold)embryonicheartswithoutanysignificantchangeinotherconfigurationsoftheactionpotential.Raisingtheconcentrationofglucoseintheexternalfluidpreventedtheshorteningoftheactionpotentialplateaubyanoxia,and,conversely,afurtherreductionwasobservedinglucose-freemedia.Inyoung(3–4daysold)embryonichearts,theshorteningoftheactionpotentialplateauwasnotproducedbyanoxia,butwasproducedbyacombinationofanoxiaandglucosedeprivation.Whentheactionpotentialwasshortenedbyanoxiainoldheartsandbyanoxiaplusglucosedeprivationinyounghearts,isoproterenol(10−5M),dibutyrylcyclic3′,5′-adenosinemonophosphate(dBcAMP:1mM)plusaminophylline(1mM),andcalciumion(3–6mM),partiallyreversedtheshortenedactionpotentialinoldhearts,butdidnotproduceanyprolongationintheyounghearts.Therefore,thecationchannelsresponsiblefortheactionpotentialplateauinyoungheartsmaybepharmacologicallydifferentfromthoseinoldhearts.Thedifferencesinactionpotentialplateaubetweenyoungandoldheartswerediscussedinrelationtodependenceuponenergy.

[学科分类] 生物科学（综合）