Involvement of deoxygenation-induced increase in tyrosine kinase activity in sickle cell dehydration

Deoxygenation of sickle (SS) cells causes cationic alterations leading to cell dehydration by various mechanisms, including activation of Ca2+-sensitive K channels and possibly of K-Cl cotransport. Since an abnormal tyrosine kinase (TK) activity exists in SS cells we investigated the possible role of tyrosine phosphorylation in SS cell dehydration. In density-fractionated SS reticulocytes and discocytes, but not in normal red cells, deoxygenation increased membrane and cytosolic TK activities and tyrosine phosphorylation of band 3, independently of external Ca2+. These effects were abolished by the TK inhibitors methyl 2,5-dihydroxycinnamate (DiOH) or tyrphostin 47 (T47). Deoxygenation-induced Ca2+ uptake was not affected by the inhibitors and Nat gain was reduced by T47 and not by DiOH. Both inhibitors decreased the loss of K+ and cellular dehydration. The effect of the inhibitors on K+ efflux was still observed in the absence of external Ca2+. These data indicate that the TK inhibitors do not interfere with deoxygenation-induced membrane permeabilization, but affect Ca2+-independent KC efflux. It cannot be excluded, however, that the TK inhibitors also attenuate Ca(2+)sensitive K+ efflux. Based on recent evidence from the literature, it is suggested that the diminution of K+ efflux results in part from inhibition of K-CI cotransport activity.