Interaction of antiarrhythmic drugs with model membranes

Several hypotheses link the molecular mechanism of action of the antiarrhythmic drugs (AAD) that belong to class I to nonspecific interactions with phospholipids sited in the neighborhood of the sodium channels in the membrane of the myocard. The interactions of asocainol (ASOC), procainamide (PROC) and quinidine (QUIN) with: (a) multibilayers of dimyristoylphosphatidylcholine (DMPC) and of dimyristoylphosphatidylethanolamine (DMPE), in both a hydrophobic and a hydrophilic medium, and (b) DMPC vesicles, were studied, respectively, by X-ray diffraction and fluorescence spectroscopy. It was found that the three AAD interacted with the lipid bilayers. However, the extension of these interactions depended on the nature and concentration of the lipids and AAD as well as on the medium where the interactions were performed. The different capacity of ASOC and PROC to perturb the bilayer structures, mainly that of DMPC, indicated that the interactions were strongly dependent on the lipophilicity of these drugs. The fact that QUIN did not completely interact in accordance to its lipophilicity suggested that other factors also play a role in these interactions. It is concluded that it may be valid the suggested molecular mechanisms of action of class I AAD involving their interaction with the membrane phospholipids.