title: Thiol-dependent passive K: Cl transport in sheep red blood cells: IX. Modulation by pH in the presence and absence of DIDS and the effect of NEM.
abstract: Recently we proposed that cytoplasmic acidification of low K+ (LK) sheep erythrocytes may stimulate ouabain-resistant Cl(-)-dependent K+ flux (K+: Cl- contransport), also known to be activated by cell swelling, treatment with N-ethylmaleimide (NEM), or removal of cellular bivalent cations. Here we studied the dependence of K+ transport on intracellular and extracellular pH (pHi, pHo) varied either simultaneously or independently using the Cl-/HCO3- exchange inhibitor 4,4, diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). In both control and NEM-treated LK cells volumes were kept near normal by varying extracellular sucrose. Using DIDS as an effective pH clamp, both K+ efflux and influx of Rb+ used as K+ congener were strongly activated at acid pHi and alkaline pHo. A small stimulation of K+ (Rb+) flux was also seen at acid pHi in the absence of DIDS, i.e., when pHi approximately pHo. Anti-Ll serum, known to inhibit K+: Cl-cotransport, prevented the pHi-stimulated K+ (Rb+) fluxes. Subsequent to NEM treatment at pH 6, K+ (Rb+) fluxes were activated only by raising pH, and thus were similar to the pH activation profile of K+ (Rb+) fluxes in DIDS-treated cells with pHo varied at constant physiologic pHi. Anti-Ll, which inhibited NEM-stimulated K+ (Rb+) fluxes, failed to do so in NEM-plus DIDS-treated cells. Thus, NEM treatment interferes with the internal but not with the external pH-sensitive site.
authors: Department of Physiology and Biophysics, Wright State University, School of Medicine, Dayton, Ohio 45401-0927.
authors: A M
authors: AM
authors: Zade-Oppen
authors: P K
authors: PK
authors: Lauf
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002021:Buffers; D002352:Carrier Proteins / Q000097:blood*; D002712:Chlorides / Q000097:blood*; D004351:Drug Resistance; D004912:Erythrocytes / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D012413:Rubidium / Q000378:metabolism; D012756:Sheep; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D027981:Symporters; D000096922:K Cl- Cotransporters
chemical_list: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D002021:Buffers; D002352:Carrier Proteins; D002712:Chlorides; D005033:Ethylmaleimide; D010042:Ouabain; D011188:Potassium; D012413:Rubidium; D013438:Sulfhydryl Compounds; D027981:Symporters; D000096922:K Cl- Cotransporters