title: Pig reticulocytes. V. Development of Rb+ influx during in vitro maturation.
abstract: Influx of the K+ analogue Rb+ was measured through the ouabain-sensitive Na+/K+ pump and the ouabain-insensitive "leak" pathways in Cl- or NO3- in mature red cells from adult pigs and in reticulocytes naturally occurring in 7-day-old piglets. In reticulocytes, Rb+ influxes by the two pathways were of about equal magnitude in Cl- (13 and 10 mmoles/liter cells X hr) and at least 25-fold larger than in mature red cells (0.5 and 0.4 mmoles/liter cells X hr). In Na+ media, a portion of the ouabain-insensitive "leak" flux of Rb+ was Cl(-)-dependent (Rb+Cl- transport) as NO3- replacement reduced Rb+ influx by 90% in reticulocytes and by 40% in mature red cells. The sulfhydryl reagent N-ethylmaleimide (NEM) stimulated Rb+Cl- transport about twofold in reticulocytes and up to 13-fold in mature red cells. When reticulocytes matured to erythrocytes during in vitro incubation, about 90% of both ouabain-sensitive Rb+ pump and ouabain-insensitive Rb+Cl- influx were lost. In contrast, the NEM-stimulated Rb+Cl- transport changed much less throughout this period, suggesting an entity operationally but not necessarily structurally distinct from the basal Rb+Cl- transport. Although the experimental variability precluded a full assessment of significant changes in the small Na+/K+ (Rb+) pump and Rb+Cl- fluxes in mature pig red cells kept for the same time period in vitro, Rb+ flux changes in reticulocytes appear to be maturational in nature, reflecting parallel activity transitions of Na+/K+ pump and Cl(-)-dependent K+ fluxes in vivo.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D004905:Erythrocyte Aging; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology; D007700:Kinetics; D008954:Models, Biological; D010042:Ouabain / Q000494:pharmacology; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism*; D012413:Rubidium / Q000097:blood*; D013552:Swine
chemical_list: D010042:Ouabain; D005665:Furosemide; D012413:Rubidium; D005033:Ethylmaleimide