SK4 Encodes Intermediate Conductance Ca²⁺-Activated K⁺ Channels in Mouse Urinary Bladder Smooth Muscle Cells

Abstract

The single channel current of intermediate conductance Ca²⁺−activated K⁺ channel(IK channel)was measured in mouse urinary bladder myocytes(MBM), and the molecular basis of the channel was suggested to be the SK4 subtype by RT−PCR.Among Ca²⁺−activated K⁺ channel subtypes(SK2, SK3, SK4 and BK), the mRNAs of SK4 and BK were predominantly expressed in MBM.IK channel currents recorded from MBM showed:38.7 pS slope conductance under symmetrical 140 mM K⁺ conditions, Ca²⁺−dependent activation, and blockade by charybdotoxin and econazole.These results strongly suggest that SK4 encodes IK channels in MBM.