Changes in membrane microviscosity associated with phagocytosis: effects of colchicine.

Abstract

The effects of phagocytosis on plasma membrane microviscosity were studied by fluorescence depolarization techniques. Lipophilic probes are apparently accumulated in intracellular vesicles to a significant degree in fibroblasts and neutrophils. Microviscosity was determined from the behavior of probes in isolated membranes. Phagocytosis of oil emulsions or polystyrene beads by rabbit polymorphonuclear leukocytes induces a marked decrease in plasma membrane microviscosity that parallels the extent of phagocytosis. Liposomes made from extracts of membrane lipid show qualitatively the same changes, indicating that the alteration of microviscosity results at least in part from changes in lipid composition. The decrease in microviscosity is abolished when colchicine is present during phagocytosis. Addition of colchicine to membranes previously isolated from control or phagocytic cells has no effect on their microviscosity. Phagocytosis is apparently accompanied by a microtubule-dependent reorganization of membrane lipids.