AJP - Cell Physiology, Vol 258, Issue 4 C622-C629, Copyright © 1990 by American Physiological Society
Loop diuretic and anion modification of NEM-induced K transport in human red blood cells
L. R. Berkowitz
Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill 27599-7035.
The thioalkylating agent N-ethylmaleimide (NEM) causes ouabain-insensitive
K loss from human red blood cells. This K loss is inhibited when
intracellular Cl is replaced by another permeant anion or when loop
diuretics are placed in the incubation medium after NEM exposure. In this
report, we have tested the possibility that Cl replacement or loop
diuretics not only influence the transport of K induced by NEM but also the
interaction of NEM with its target sulfhydryl group. This possibility was
examined by replacing intracellular Cl or exposing the cells to loop
diuretics before NEM exposure, then measuring K loss in a Cl medium free of
loop diuretics. We found that such pretreatment with either Cl substitution
or loop diuretics stimulated, rather than inhibited, NEM-induced K loss.
This enhancement was not additive in that the increase in K loss induced by
anion substitution was not increased further when loop diuretics were also
present. These data suggest that anion substitution and loop diuretics
enhance the interaction of NEM with its cellular target but inhibit the K
loss induced by NEM.
