Effect of Concanavalin A on Membrane Potential of Polymorphonuclear Leukocyte Monitored by Fluorescent Dye

Abstract

Changes in fluorescence intensity of the dye 3,3''-dipropylthiodicarbocyanine iodide were monitored in guinea pig polymorphonuclear leukocytes (PMN) in the presence of reagents that modulate plasma membrane dynamics. Valinomycin, a specific K+ ionophore, increased fluorescence intensity as a function of log K+ concentration in incubation medium. The fluorescence was intensified by treating cells with concanavalin A and 100 .mu.g/ml of the lectin was required for a half maximum change. The change was temperature dependent. It was inhibited by potent depressants of of membrane fluidity, such as cholesterol ester and cepharanthine, or by colchicine which degrades microtubules. Cytochalasin B which degrades microfilament assembly stimulated fluorescence change. The change was also dependent on the ionic environment and energy state of PMN. The fluidity of the surface membrane and cytoskeletal system are probably closely related to changes in PMN membrane potential. The data further suggest that the changes might be involved in the concanavalin A-related transmembrane control mechanism.