Membrane stabilizing action of NCO-650 and its congeners.

NCO-650 and its congeners and two other antiallergics, disodium cromoglycate and tranilast, were studied to determine the degree of protection of rat erythrocytes against hypotonic hemolysis, the reduction of the surface tension of dipalmitoylphosphatidylcholine (DPPC) monolayer and the depression of the phase-transition temperature of DPPC liposome bilayers. NCO-650 was found to show the greatest hemolysis protection, reduction of the surface tension and depression of the phase-transition temperature, indicating that it possesses a significant affinity to cell membranes and a significant ability to stabilize cell membranes. Disodium cromoglycate and tranilast showed neither cell membrane affinity nor hemolysis protection, although they inhibit histamine release from mast cells like NCO-650 and its congeners. The significant membrane stabilizing action of NCO-650 must be related, at least in part, to its extraordinarily high lipid solubility.