Na+-K+ pump activities of high- and low-potassium sheep red cells with internal magnesium and calcium altered by A23187.
AUTOR(ES)
Fujise, H
RESUMO
1. Sheep erythrocytes were treated with the divalent metal ionophore A23187 to alter the cellular magnesium (Mgi) and calcium (Cai) composition. Ouabain-sensitive Na+-K+ pump fluxes were measured using rubidium as a potassium congener in media where Cl- was replaced by NO3-. 2. A23187, per se, had no effect on ouabain-sensitive rubidium influx. However, lowering the concentration of cellular magnesium [( Mg]i) and increasing that of calcium [( Ca]i) decreased Na+-K+ pump flux. 3. Ouabain-sensitive rubidium influx was found to be a saturating function of [Mg]i in high-potassium (HK) red cells with a Hill coefficient of about 1.8 and an apparent half-activation constant (K0.5) of 0.46 mmol/(l original cells). In low-potassium (LK) cells, in the absence and presence of the Na+-K+ pump stimulatory L-antibody, ouabain-sensitive rubidium influx was also saturated with Mgi yielding Hill coefficients of close to 1.8 and K0.5 values of 0.20 and 0.30 mmol/(l original cells), respectively. 4. When [Ca]i was raised at constant [Mg]i ouabain-sensitive rubidium influx was inhibited at about 700 mumol/(l cells) in both HK, and in anti-L-treated LK red cells. 5. These data exclude the possibility that the Na+-K+ pump turnover, known to be different in HK red cells, and in LK red cells in the absence and presence of anti-L (Joiner & Lauf, 1978b), is based on differences in the activation by MgATP, and that Cai interacts with the Na+-K+ pump cycle differently in the two red cell cation types.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1190994Documentos Relacionados
- Properties of the Na+-K+ pump in human red cells with increased number of pump sites.
- Potassium transport across rat alveolar epithelium: evidence for an apical Na+-K+ pump.
- Relation between Na+-K+ pump, Na+ activity and force in strophanthidin inotropy in sheep cardiac Purkinje fibres.
- Functionally Abnormal Na+-K+ Pump in Erythrocytes of a Morbidly Obese Patient
- Potassium translocation by the Na+/K+ pump is voltage insensitive.