Activation of Cl-dependent K transport in Ehrlich ascites tumor cells.
N-ethylmaleimide (NEM) treatment of steady-state Ehrlich cells induces a substantial net loss of cellular KCl and cell shrinkage. The majority of the initial K loss is Cl dependent. From estimates of membrane potential it is concluded that the NEM-induced KCl loss is electroneutral. The effect of NEM on H extrusion by cells in 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-containing medium showed that only an insignificant part of the K loss could be attributed to an activation of a K-H exchange system. Consequently, NEM appears to activate a K-Cl cotransport, which causes cell shrinkage. The anion preference of the K loss is Cl greater than Br much greater than SCN = NO3. NEM also seems to inhibit a Cl-dependent Na uptake previously described in shrunken cells. Addition of NEM to cells undergoing regulatory volume decrease after swelling in hyposmotic media results in a Cl-dependent acceleration of cell shrinkage, suggesting that a Cl-dependent component of K efflux is induced by NEM also in swollen cells. A Cl-dependent K efflux is also activated in Ca-depleted cells or at reduced extracellular pH after cell swelling. Under isotonic conditions activation of Cl-dependent K flux after Ca depletion or pH reduction could not be demonstrated. The combined results show that Ehrlich cells possess a latent K-Cl cotransport that becomes active after changes in the state of SH groups, regardless of the initial cell volume. A similar K-Cl cotransport is activated in hypotonically swollen cells after Ca depletion or after reduction of the extracellular pH.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001693:Biological Transport, Active; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology*; D005033:Ethylmaleimide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism*; D011189:Potassium Chloride / Q000378:metabolism
D002712:Chlorides; D000001:Calcimycin; D011189:Potassium Chloride; D005033:Ethylmaleimide; D011188:Potassium; D002118:Calcium