title: Thiol-dependent passive K/Cl transport in sheep red cells: II. Loss of Cl- and N-ethylmaleimide sensitivity in maturing high K+ cells.
abstract: A fraction of the passive, ouabain-insensitive K+ fluxes in mature low Kr(LK) but not in high K+ (HK) sheep red cells requires the presence of Cl- anions and can be stimulated by volume expansion (Dunham, P.B., Ellory, J.C., J. Physiol (London) 318:511-530, 1981) or treatment with 2 mM N-ethylmaleimide (NEM) (Lauf, P.K., Theg., B.E., Biochem. Biophys. Res. Commun. 92:1422-1428, 1980). In the present study it is shown that reticulocytes of both anemic LK and HK sheep possess the Cl- -dependent K+ transport system which subsequently remains functional in mature LK but not in HK red cells. Kinetically, Cl- -mediated K+ fluxes of reticulocytes of LK sheep are different from mature red cells only in their Vmax values as measured in Na+ or choline+ media, while there is an apparently much lower affinity for external K+ ions in reticulocytes of HK sheep. N-ethylmaleimide stimulated K+ transport in the reticulocytes of both sheep genotypes suspended in Cl- but failed to do so in NO3- media. The data are interpreted in terms of their biochemical, physiologic, and genetic implications for the HK/LK transition in sheep red cells.
mesh_terms: D000740:Anemia / Q000097:blood; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000097:blood* / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology*; D066298:In Vitro Techniques; D009566:Nitrates / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D012156:Reticulocytes / Q000378:metabolism; D012756:Sheep; D012964:Sodium / Q000097:blood
chemical_list: D002712:Chlorides; D009566:Nitrates; D012964:Sodium; D005033:Ethylmaleimide; D011188:Potassium