The plasma-membrane internalization and recycling is enhanced in macrophages upon activation with gamma-interferon and lipopolysaccharide; a study using the fluorescent probe trimethylaminodiphenylhexatriene.

The lipophilic fluorescent probe trimethylaminodiphenylhexatriene (TMA-DPH), previously used as a plasma membrane marker in membrane fluidity and exocytosis studies, was shown, to monitor the plasma-membrane internalization-recycling shuttle movement in cells. Using this approach we present here kinetic and dose-response data, which give evidence that the plasma membrane flow is enhanced in bone marrow macrophages from various mouse strains, upon in vitro activation with gamma interferon (IFN-gamma) or bacterial lipopolysaccharide (LPS), within physiological dose ranges. The effect studied evolved in line with the usual development kinetics of macrophage activation. Complementary assays on membrane fluidity, surface charge density and membrane surface indicated no related changes. From these experiments it is concluded that the observed enhancement of the plasma membrane traffic does not originate from specific limited membrane modifications, but is merely a particular feature of the overall macrophage activation.