[Comparative studies on the chemical modifications of Ehrlich ascites tumor cell membranes by hydrophobic drugs (cepharanthine, papaverine and cholesterol) (author's transl)].

Comparative studies were done on the actions of hydrophobic drugs (cepharanthine, papaverine and cholesterol) regarding chemical modifications of Ehrlich ascites tumor cell membranes. Changes in membrane potential monitored by using cyanine dye (diS-C3-(5)) were induced by cepharanthine and papaverine, but not by cholesterol. Increase in membrane permeability of K+ ions induced with lysolecithin was strongly inhibited in the order of papaverine, cholesterol and cepharanthine. Oxygen uptake by the cells was also strongly inhibited by papaverine, but the inhibitory effect by cepharanthine was little and cholesterol had no effect. Membrane fluidity was decreased in the order of cholesterol, cepharanthine and papaverine. From these results, it was suggested that papaverine maintained the compartmentation of K+ ion and membrane fluidity by regulating the intracellular mitochondrial metabolism or by inhibiting the membrane bound ATPase nucleotidase activity. The membrane stabilizing effect of cepharanthine and cholesterol probably was due to decrease in the membrane fluidity because of the hydrophobic association to the lipid bilayer of the cell membranes.