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 Ca 2+-sensitive K channels and possibly of K-Cl cotransport. Since an abn ormal 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 n ormal red cells, deoxygenation increased membrane and cytosolic TK act ivities and tyrosine phosphorylation of band 3, independently of exter nal Ca2+. These effects were abolished by the TK inhibitors methyl 2,5 -dihydroxycinnamate (DiOH) or tyrphostin 47 (T47). Deoxygenation-induc ed Ca2+ uptake was not affected by the inhibitors and Nat gain was red uced by T47 and not by DiOH. Both inhibitors decreased the loss of Kand cellular dehydration. The effect of the inhibitors on K+ efflux wa s still observed in the absence of external Ca2+. These data indicate that the TK inhibitors do not interfere with deoxygenation-induced mem brane permeabilization, but affect Ca2+-independent KC efflux. It cann ot be excluded, however, that the TK inhibitors also attenuate Ca(2+)s ensitive K+ efflux. Based on recent evidence from the literature, it i s suggested that the diminution of K+ efflux results in part from inhi bition of K-CI cotransport activity.