Pyrene fluorescence: a potential tool for estimation of short-range lateral mobility in membranes of living renal epithelial cells.

The excimer-to-monomer (E/M) fluorescence ration of pyrene (p) and its derivatives has been found to correlate with membrane fluidity. We explored the possible use of this method in living renal epithelial cells. In Modin-Darby canine kidney cells, successful fluorescent labeling was obtained with p-cholesterol, p-trimethylammonium (TMA), p-sulfonamidethyl-TMA, p-butyrate, p-propanoate or p-dodecanoate. Among them, the labeling with p-cholesterol was most stable. The whole cell cholesterol content did not significantly increase after loading p-cholesterol and the probe incorporated was not degraded. The E/M ratio changed reproducibly and significantly by temperature change, a standard method to alter membrane fluidity. Thus, the E/M ratio of p-cholesterol fluorescence is suggested to be a potential parameter of membrane fluidity in living renal epithelial cells and might be useful in investigating the relationship between the physical state of the membrane and epithelial function.