title: Evidence for bumetanide-sensitive, Na(+)-dependent, partial Na-K-Cl co-transport in red blood cells of a primitive fish.
abstract: Tracer uptake studies identified the major routes for K+ transport in hagfish red cells, resolving them into ouabain-sensitive, loop diuretic-sensitive, and residual components. The K1/2 values for ouabain, bumetanide, and furosemide were 10(-5), 6 x 10(-7), and 5 x 10(-6) M, respectively. The properties of the Na-K-Cl co-transporter were investigated further by varying K+, Na+, and Cl- concentrations. The measured K1/2 values were similar to those for human red cells. Finally, the stoichiometry of Na:K:Cl uptake was determined, giving 1:1 for K+:Cl-; in contrast, no significant Na+ flux could be measured, although Na+ content must be present for measurable bumetanide-dependent K+ or Cl- flux to occur. The Na-K-Cl transport therefore shows Na(+)-dependent KCl co-transport or partial flux of the system.
authors.affiliation: University Laboratory of Physiology, Oxford, England.
authors.forename: J C
authors.initials: JC
authors.lastname: Ellory
authors.forename: M W
authors.initials: MW
authors.lastname: Wolowyk
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology*; D002712:Chlorides / Q000097:blood*; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D006196:Hagfishes / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D012414:Rubidium Radioisotopes; D012964:Sodium / Q000097:blood / Q000502:physiology*
chemical_list: D002712:Chlorides; D012414:Rubidium Radioisotopes; D002034:Bumetanide; D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D011188:Potassium