Single chloride-permeable channels of large conductance in cultured cardiac cells of new-born rats.
Large conductance channels were observed in the membrane of cultured cardiac cells of newborn rats studied with the patch-clamp technique in cell-attached and inside-out configurations. These channels were observed in approximately equal to 4% of the patches. In the cell-attached configuration they exhibited outward rectification and partial inactivation. In the inside-out configuration no rectification occurred but inactivation was present, mainly during hyperpolarizations. Two channels with large single unit conductances (400-450 pS) and one with a smaller conductance (200-250 pS) were frequently observed in the same patch. The two large channels generally had different kinetics. Under steady-state conditions the opening probability of the faster channel appeared to be voltage-independent. The slower channel was activated by depolarization. In asymmetrical solutions the permeability ratios PNa/PCl were 0.03 and 0.24 for the larger and smaller channels, respectively; corresponding values for PBa/PCl were 0.04 and 0.09. It is proposed that in cardiac membranes the chloride permeability system is composed of widely dispersed microclusters forming grouped channels of different types and sizes.
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D004553:Electric Conductivity; D006321:Heart / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials; D051381:Rats; D016276:Ventricular Function
D002712:Chlorides; D007473:Ion Channels