Inhibition of “spontaneous,” notochord-induced, and collagen-induced in vitro somite chondrogenesis by cyclic AMP derivatives and theophylline☆

[摘要] ThepresentstudyrepresentsafirststepininvestigatingthepossibleinvolvementofcyclicAMPinthestimulationofsomitechondrogenesiselicitedbyextracellularmatrixcomponentsproducedbytheembryonicnotochord.DibutyrylcyclicAMP(db-cAMP)at1.0mMseverelyimpairs“spontaneous”somitechondrogenesis,i.e.,inhibitstheformationofthesmallamountofcartilaginousmatrixnormallyformedbyembryonicsomitesinvitrointheabsenceofinducingtissues.Thisinhibitionofcartilaginousmatrixformationisreflectedina30–40%reductioninsulfatedglycosaminoglycan(GAG)accumulation.8-Bromo-cyclicAMPalsoseverelyinhibitscartilageformationandsulfatedGAGaccumulationbysomiteexplants.ThisimpairmentislimitedtocyclicAMPderivatives;dibutyrylcyclicGMP,5′-AMP,and2′,3′-AMPhavenoeffect.TheinhibitoryeffectofcyclicAMPderivativesismimickedbythecyclicAMP-phosphodiesteraseinhibitor,theophylline,andpotentiatedbytheadditionofbothdb-cAMPandtheophylline.DibutyrylcyclicAMPand/ortheophyllinealsoinhibitthestimulationofcartilaginousmatrixformationandsulfatedGAGaccumulationnormallyelicitedbytheembryonicnotochord,reducingaccumulationtoalevelsimilartothatfoundinsomiteexplantswithoutnotochord.TheinhibitionofchondrogenesisbycyclicAMPinnotochord-somiteexplantsappearstoresultfromaninabilityofsomitestorespondandnotfromaneffectontheinductivecapacityofthenotochord,sincedb-cAMPhasnodetectableeffectonthesynthesisofmolecules(sulfatedGAGandcollagen)bythenotochordthathavebeenimplicatedinitsinductiveactivity.Finally,db-cAMPand/ortheophyllineinhibitthestimulationofsomitechondrogenesisnormallyelicitedbypurifiedTypeIcollagensubstrates.DibutyrylcyclicAMPandtheophyllinereducesulfatedGAGaccumulationbysomitesculturedoncollagentoalevelevenbelowthataccumulatedbysomitesculturedintheabsenceofcollagen,i.e.,onMilliporefilters.

[学科分类] 生物科学（综合）