Passive potassium transport in LK sheep red cells. Modification by N-ethyl maleimide.
Passive K transport, as modified by N-ethyl maleimide (NEM), was studied in erythrocytes of the low-K (LK) phenotype of sheep. Brief (5-min) treatment with NEM at less than 0.5 mM caused inhibition of passive K influx; NEM at concentrations greater than 0.5 mM caused stimulation of K influx. NEM had similar effects on K efflux. The treatments with NEM did not affect cell volumes (passive K transport in LK cells is sensitive to changes in cell volume). The stimulation of K transport by high [NEM] was also not a consequence of an effect on the metabolic state of the cells. Passive K transport in LK cells is dependent on Cl (it is inhibited in Cl-free media; it may be K/Cl cotransport). NEM had no effect on K influx in Cl-free (NO3-substituted) media. Pretreatment of the cells with anti-L antiserum (L antigen is found on LK cells and not on HK cells) prevented stimulation of K influx by NEM, but did not prevent inhibition. Therefore, NEM modifies the Cl-dependent K transport pathway at two separate sites, a low-affinity site, at which it stimulates, and a high-affinity site, at which it inhibits. Anti-L antibody prevents NEM's action, but only at the low-affinity site.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004347:Drug Interactions; D004911:Erythrocyte Volume / Q000187:drug effects; D004912:Erythrocytes / Q000276:immunology / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology*; D007106:Immune Sera / Q000276:immunology; D007460:Iodoacetamide / Q000494:pharmacology; D009994:Osmolar Concentration; D010641:Phenotype; D011188:Potassium / Q000097:blood*; D012756:Sheep / Q000097:blood*; D012964:Sodium / Q000378:metabolism; D013997:Time Factors
D007106:Immune Sera; D012964:Sodium; D005033:Ethylmaleimide; D011188:Potassium; D007460:Iodoacetamide