SENSITIVITYTO FLOW OF INTRINSICGATING ININWARDLY RECTIFYINGPOTASSIUMCHANNEL FROM MAMMALIAN SKELETAL MUSCLE

SUMMARY 1.Current through inwardly rectifying K+channels wasmeasured ininside-out patches fromratandhumansarcolemmal vesicles andfromdispersed ratflexor digitorum brevis muscle fibres. Thepatches werepositioned soasto face theaperture ofalarge-diameter pipette fromwhichsolution ofthesamecomposition asthebath solution could beejected. Thesolution within thepatchpipette andthebathsolution bothcontained principally 140mM-KCl. 2.Thekinetic behaviour oftheinwardly rectifying channel wasfoundtovary according towhether thepatch wasinstatic orflowing solution. Atnegative holding potentials, whenthechannel isopenmostofthetimeinstatic solution, flow produced areversible andrepeatable decrease inopenprobability. 3.InMg2+-free solution theinwardly rectifying channel allows outward current to passatpositive holding potentials. Thisallows thekinetic behaviour ofthechannel instatic andflowing solution tobecompared overawider voltage range. 4.Inbothstatic andflowing solution, theopenprobability-voltage relation is sigmoidal andcanbefitted byaBoltzmann curve. Asaresult offlow, themaximum openprobability atnegative potentials isdecreased andthemid-point oftherelation isshifted totheright bymorethan20mV. 5.Noevidence could befoundfortheexistence ofalocal concentration gradient sensitive toflow. Application ofsuction tothepatchpipette showedtheinwardly rectifying channels nottobesensitive tomembranestretch. Thepossibility is contemplated thatshear stress upontheinner faceofthepatch modulates thekinetic behaviour ofthechannel. 6.Incontrast totheinwardly rectifying K+channel, neither theCa2+-activated K+channel northeATP-regulated K+channel aresensitive toflow.