Thiol-dependent passive K: Cl transport in sheep red blood cells: X. A hydroxylamine-oxidation induced K: Cl flux blocked by diethylpyrocarbonate.

Hydroxylamine, a potent oxidizing agent used to reverse carbethoxylation of histidine by diethylpyrocarbonate, activated Cl-dependent K flux (K: Cl cotransport) of low K sheep red blood cells almost sixfold. When K: Cl cotransport was already stimulated by N-ethylmaleimide, hydroxylamine caused an additional twofold activation suggesting modification of sites different from those thiol alkylated. This conclusion was supported by the finding that hydroxylamine additively augmented also the diamide-induced K: Cl flux (Lauf, P.K. 1988. J. Membrane Biol. 101: 179-188) with dithiothreitol fully reversing the diamide but not the hydroxylamine effect. Stimulation of K: Cl cotransport by hydroxylamine was completely inhibited by treatment with diethylpyrocarbonate also known to prevent K: Cl cotransport stimulation by N-ethylmaleimide, both effects being independent of the order of addition. Hence, although the effect of carbethoxy modification of K: Cl flux cannot be reversed by hydroxylamine and thus excludes histidine as the target for diethylpyrocarbonate, our finding reveals an important chemical determinant of K: Cl cotransport stimulation by both hydroxylamine oxidation and thiol group alkylation.