A fluorescence anisotropy study of stabilizing effect of tri- and tetra- nitrovasodilatory drugs on DPPC liposomal membrane

Abstract

Glyceryl trinitrate (GT) and pentaerythritol tetranitrate (PT) are two vasodilatory drugs. The physical properties of the membrane lipid matrix, which determine the structure and function of the membrane-bound proteins, generally control the pertubation mechanism of these drugs. Thus, physical interaction of these drugs with membrane lipids is very crucial for their clinical use, different cellular processes, as well as for targetted drug delivery systems. In the present paper, we have reported for the first time the interaction between these drugs and the lipid molecules in the liposomal system of dipalmitoylphosphatidylcholine (DPPC), as measured by steady-state fluorescence anisotropy using 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescent probe. Our results show that by dissolving in the lipid matrix these two drugs effectively stabilise the liposomal membrane: the effect being more in case of GT than in PT, indicating that the rigidifying effect is independent of the number of nitrate groups of the two drugs. This effect increases with the increase in drug concentration, implying solubilisation of all drug molecules. Though our in vitro study has more physical significance than a physiological one, the results obtained here may be used to interpret the effects that are observed in vivo.