An effect of chloride on (Na+K) co-transport in human red blood cells.

In certain conditions, internal K can stimulte active Na:K transport as well as Na:Na exchange through the ouabain-sensitive Na, K exchange pump. When the exchange was examined during a study of the action of internal K, it emerged that the removal of K0 (the main requirement for Na:Na exchange) reduced the ouabain-insensitive Na efflux. Thus, in eight experiments done variously with outdated cells or high and low [K]i, PCMBS-treated cells, the K0-dependent Na efflux ranged from 0.18 to 0.70 muEquiv per ml cells per h. This conflicts with the well established view that the K0-dependent and ouabain-sensitive components of Na efflux are identical. However, the K0-dependent, ouabain-insensitive Na efflux was found to go through the (Na+K) co-transport system, which was further found to show a dependence on chloride ions.