Na+-K+ pump activities of high- and low-potassium sheep red cells with internal magnesium and calcium altered by A23187

• Published in: The Journal of physiology 1988-11, Vol.405 (1), p.605-614
• Main Authors: Fujise, H, Lauf, P K
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biological Transport, Active - drug effects; Calcimycin - pharmacology; Calcium - blood; Cell physiology; Erythrocytes - metabolism; Fundamental and applied biological sciences. Psychology; Magnesium - blood; Molecular and cellular biology; Ouabain - pharmacology; Potassium - blood; Rubidium - blood; Sheep; Sodium - blood
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1988.sp017351

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.