A FLUORESCENCE ANISOTROPY STUDY OF STABILIZING EFFECT OF TRI-NITROVASODILATORY AND TETRA-NITROVASODILATORY DRUGS ON DPPC LIPOSOMAL MEMBRANE

Glyceryl trinitrate (GT) and pentaerythritol tetranitrate (PT) are two vasodilatory drugs. The physical properties of the membrane lipid mat rix, which determine the structure and function of the membrane-bound proteins, generally control the perturbation mechanism of these drugs. Thus, physical interaction of these drugs with membrane lipids is ver y crucial for their clinical use, different cellular processes, as wel l as for targetted drug delivery systems. In the present paper, we hav e reported for the first time the interaction between these drugs and the lipid molecules in the liposomal system of dipalmitoylphosphatidyl choline (DPPC), as measured by steady-state fluorescence anisotropy us ing 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescent probe. Our resu lts show that by dissolving in the lipid matrix these two drugs effect ively stabilise the liposomal membrane: the effect being more in case of GT than in PT, indicating that the rigidifying effect is independen t of the number of nitrate groups of the two drugs. This effect increa ses with the increase in drug concentration, implying solubilisation o f all drug molecules. Though our in vitro study has more physical sign ificance than a physiological one, the results obtained here may be us ed to interpret the effects that are observed in vivo.