Reconstitution and characterization of a calcium-activated channel from heart

This paper is the first description of a calcium-activated nonspecific cation channel in adult ventricular muscle. We report gating kinetics and ionic selectivity data from experiments performed at the single channel level. Calcium activation is described by a gating model wherein two ions are involved in the reaction. Channel gating exhibited marked voltage dependence. Ionic selectivity experiments indicated that the channel is cation-selective but unable to discriminate between Na⁺ and K⁺. We discuss evidence that this channel mediates transient inward current in ventricular tissue; thus, the channel may be involved in afterdepolarization-induced cardiac arrhythmias.