Berkowitz L R
Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill 27599-7035.
Am J Physiol. 1990 Apr;258(4 Pt 1):C622-9. doi: 10.1152/ajpcell.1990.258.4.C622.
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.
硫烷基化试剂N - 乙基马来酰亚胺（NEM）会导致人红细胞出现哇巴因不敏感的钾离子流失。当细胞内的氯离子被另一种可通透阴离子取代时，或者在NEM暴露后将袢利尿剂置于孵育培养基中时，这种钾离子流失会受到抑制。在本报告中，我们测试了氯离子替代或袢利尿剂不仅会影响NEM诱导的钾离子转运，还会影响NEM与其靶巯基相互作用的可能性。通过在NEM暴露前替代细胞内的氯离子或将细胞暴露于袢利尿剂中，然后在不含袢利尿剂的氯离子培养基中测量钾离子流失来检验这种可能性。我们发现，用氯离子替代或袢利尿剂进行这种预处理会刺激而非抑制NEM诱导的钾离子流失。这种增强作用并非相加性的，因为当同时存在袢利尿剂时，阴离子替代诱导的钾离子流失增加并未进一步增加。这些数据表明，阴离子替代和袢利尿剂会增强NEM与其细胞靶点的相互作用，但会抑制NEM诱导的钾离子流失。
