MOLECULAR-INTERACTIONS OF QUINIDINE WITH PHOSPHOLIPID-BILAYERS

Quinidine (QUIN) is one of the most important and efficient antiarrhyt hmic drugs (AAD). It belongs to class I, which are the drugs that exer t their action at the level of the sodium channels in the membrane of the myocard. Several hypotheses support the idea that the molecular me chanism of action of the AAD is via nonspecific interactions with phos pholipids sited in the neighborhood of the channels. In order to probe the validity of these hypotheses, QUIN was made to interact with the phospholipids dimyristoylphosphadidylcholine (DMPC) and dimyristoylpho sphatidylethanolamine (DMPE). These interactions were performed in a h ydrophobic and a hydrophilic medium under a wide range of molar ratios . The resulting products were analyzed by X-ray diffraction. QUIN solu tions were also made to interact with DMPC liposomes, which were studi ed by fluorescent spectroscopy. Finally human erythrocytes which were incubated with QUIN solutions were observed by scanning electron micro scopy. The results of these experiments proved that QUIN indeed intera cted with phospholipid bilayers.