Transmembrane potential changes during phagocytosis in rat alveolar macrophages

Studies were carried out to measure changes in the transmembrane potential of rat alveolar macrophages during exposure of the cells to zymosan particles or to the membrane perturbant, phorbol-12-myristate-13-acetate (PMA), and to determine if changes in membrane potential are related to superoxide anion release. Exposure of the cells to either zymosan or PMA leads to membrane depolarization, which precedes superoxide anion release. Furthermore, the magnitude of the depolarization is dependent upon the concentration of either zymosan or PMA. During exposure of the alveolar macrophages to increasing levels of zymosan, there is an increase in the amount of superoxide released as well as an increase in the magnitude of the depolarization. Incubation of the cells in medium containing 150 mM K+, a medium which causes membrane depolarization, leads to superoxide release from resting cells and a decrease in the amount of superoxide released from cells exposed to zymosan. These results indicate that release of superoxide anion from rat alveolar macrophages is related to membrane depolarization and suggest that the transmembrane potential change may act as a signal to initiate the phagocytotic responses of the cells.