THE INVOLVEMENT OF THE CA-DEPENDENT K-CHANNEL AND OF THE KCL COTRANSPORT IN SICKLE-CELL DEHYDRATION DURING CYCLIC DEOXYGENATION

We have investigated the mechanisms involved in sickle cell dehydratio n upon continuous or cyclic deoxygenation: the Ca2+-actived K+ channel and the KCl co-transport system. Short-term continuous deoxygenation (1 h) of sickle cells in a Ca2+-containing medium promoted a stimulati on of the efflux of K+ and cell dehydration. This latter was reduced b y the replacement of Ca2+ in the medium by EGTA, but not by addition o f [(dihydro indenyl)oxy] alkanoic acid (DIOA), an inhibitor of the KCl co-transport. During cycles of deoxygenation-reoxygenation, cell dehy dration was partly prevented by EGTA and significantly reduced by DIOA only in the presence of Ca2+. The present data support the view that sickle cell dehydration during deoxygenation arises from the stimulati on of the Ca2+-dependent K+ permeability leading to water loss, wherea s during reoxygenation periods, subsequent activation of the KCl co-tr ansport also contributes to cell dehydration.