The use of fluorescamine as a permeant probe to localize phosphatidylethanolamine in intact friend erythroleukaemic cells.

Intact Friend erythroleukaemic cells (Friend cells) were incubated at 0-4 degrees C with increasing amounts of fluorescamine. Phospholipids were extracted and the amounts of phosphatidylethanolamine and of its fluorescamine derivative were determined. (1). The plasma membrane of intact Friend cells appeared to be permeable to fluorescamine in a concentration-dependent way. (2). Three pools of phosphatidylethanolamine could be detected as the fluorescamine concentration was raised. The two first pools were ascribed to the outer monolayer (16-17% of the total cellular phosphatidylethanolamine) and inner (17-18%) monolayer of the plasma membrane, respectively, indicating an essentially symmetrical distribution of this phospholipid. The third pool of phosphatidylethanolamine (66%) corresponds to the contribution of intracellular membranes. (3). These data were used in turn, to calculate the relative amount of each phospholipid class present in the plasma membrane. The results are in perfect agreement with those obtained by an independent method involving the use of sphingomyelinase C (Rawyler, A., Roelofsen, B., Op den Kamp, J.A.F. and Van Deenen, L.L.M. (1983) Biochim. Biophys. Acta 730, 130-138). The present method is discussed in terms of its applicability for the localization of phosphatidylethanolamine in eukaryotic cells.