THE ROLE OF THE SODIUM-PUMP IN THE PLASMA-MEMBRANE POTENTIAL CHANGES DURING MAST-CELL ACTIVATION

The role of the sodium pump in the plasma membrane potential changes induced by compound 48/80 and by antigenic challenge has been investigated using a fluorescent potential sensitive probe, bis-oxonol. Compound 48/80 induced a fast decrease of the fluorescence of bis-oxonol followed by a delayed decrease. The antigenic stimulation induced only a delayed decrease of fluorescence. Zinc gluconate inhibited the first decrease but did not alter the second one. The delayed decrease was inhibited by ouabain or by the absence of potassium. These results suggest that compound 48/80 induced mast cell secretion via a zinc-sensitive mechanism followed by activation of the sodium pump. The changes in the plasma membrane potential during the antigenic stimulation are due to the activation of the sodium pump but occur after the secretion process.