title: Sodium and potassium transport in trout (Salmo gairdneri) erythrocytes.
abstract: The principal pathways of Na+ and K+ transport in trout erythrocytes have been characterized. Approximately 50% of K+ influx in steady-state erythrocytes was inhibited by ouabain (1 mM) and 46% by furosemide (1 mM). Furosemide-sensitive K+ influx was a saturable function of external K+ concentration with a Km of 25 mM. This flux component was also inhibited by SITS (4-acetamido-4'-isothiocyanatostilbene-2'2-disulphonate) (concentration required for 50% inhibition, I50 = 7.6 X 10(-6)M) and by the removal of external Cl-. An increase in cell volume stimulated furosemide-sensitive K+ influx and cell shrinkage inhibited this flux. K+ efflux was mainly furosemide-sensitive (64% of total). This pathway was unaffected by variations in extracellular K+ concentration and is therefore not exchange diffusion. However, it was affected by variations in cell volume in a similar way to the furosemide-sensitive K+ influx. Na+ influx was only slightly sensitive to furosemide (13% of total) but this component was very sensitive to changes in cell volume; decreased cell volume increased Na+ influx whilst increased cell volume inhibited Na+ influx. Furosemide-sensitive K+ influx was unaffected by variations in external Na+ concentration. Similarly, furosemide-sensitive Na+ influx was unaffected by variations in external K+ concentration. This indicates that the passive influxes of Na+ and K+ were not coupled, in contrast to the situation in avian erythrocytes. The opposite effects of cell volume upon passive Na+ and K+ fluxes are in good agreement with the net movements of these cations during volume regulation in erythrocytes of the flounder (Cala, 1977) and the toadfish (Lauf, 1982).
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D066298:In Vitro Techniques; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood* / Q000494:pharmacology; D012487:Salmonidae / Q000097:blood*; D012964:Sodium / Q000097:blood*; D014337:Trout / Q000097:blood*
chemical_list: D002712:Chlorides; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D011188:Potassium