Antibody-induced alterations in the kinetic characteristics of the Na:K pump in goat red blood cells.
The kinetic characteristics of the Na:K pump in high potassium (HK) and low potassium (LK) goat red cells were investigated after altering the intracellular cation concentrations. At low concentrations of intracellular K (K(c)), increasing K(c) at first stimulates the active K influx in HK cells, but at higher K(c) the pump is inhibited. These results suggest that in HK cells K(c) acts both at a stimulatory site at the inner aspect of the pump and by competition with intracellular Na (Na(c)) at the Na translocation sites. In LK cells, K(c) inhibits the active K influx and the sensitivity of LK cells to inhibition is much greater than the sensitivity of HK cells. Exposure of LK cells to an antibody (anti-L), raised in an HK sheep by injection of LK sheep cells, increased the active K influx at any given K(c). The effect of the antibody was greater at higher intracellular K concentrations, and in cells with very low concentrations of K the antibody had little effect on the pump rate. The failure of anti-L to stimulate the pump in low K(c) LK cells was not due to failure of the antibody to bind to the cells. Anti-L combining at the outer surface of the cell reduces the affinity of the pump at the inner surface for K at the inhibitory sites. The maximal pump rate in LK cells at optimal Na and K concentrations is less than the maximal pump rate of HK cells under the same circumstances.
D000818:Animals; D000937:Antigen-Antibody Reactions; D001666:Binding Sites, Antibody; D004912:Erythrocytes / Q000276:immunology / Q000378:metabolism*; D005828:Genetics, Population; D006041:Goats; D007106:Immune Sera; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D012756:Sheep / Q000276:immunology; D012964:Sodium / Q000378:metabolism*
D007106:Immune Sera; D010042:Ouabain; D012964:Sodium; D011188:Potassium