Acetylcholine receptor channels are present in undifferentiated satellite cells but not in embryonic myoblasts in culture☆

摘要

Theexpressionandthephysiologicalpropertiesofacetylcholinereceptors(AChRs)ofmononucleatedmyogeniccells,isolatedfromeitherembryonicoradultmuscleofthemouse,havebeeninvestigatedusingthegigaohmsealpatch-clamptechniqueincombinationwithimmunocytochemistry(withananti-myosinantibody)and?±-bungarotoxinbindingtechniques.Undifferentiated(myosin-negative)embryonicmyoblasts,growneitherinmasscultureorunderclonalconditions,werefoundtobeunresponsivetoAChanddidnotbind?±-bungarotoxin.Onthecontrary,undifferentiatedsatellitecells(fromadultmuscle)exhibitedchannelsactivatedbyAChand?±-bungarotoxinbindingsitessimilartothoseobservedindifferentiated(myosin-positive)embryonicmyoblastsandmyotubes.TwoclassesofACh-activatedchannelswithdifferentopeningfrequencieswereidentified.Themajorclassofchannelshadaconductanceofabout42pSandmeanopentimeof3.1a€“8.2msec.Theminorclassofchannelshadsmallerconductance(about17pS)andsimilaropentime.Duringdifferentiation,theconductanceofthetwochannelsdidnotchangesignificantly,whilechannellifetimebecameshorterinmyotubesderivedfromsatellitecellsbutnotinmyotubesderivedfromembryonicmyoblasts.Therelativeproportionofsmalloverlargechannelswassignificantlylargerinembryonicthaninadultmyogeniccells.