X-RAY STUDIES ON PHOSPHOLIPID-BILAYERS .14. INTERACTIONS WITH THE ANTIARRHYTHMIC ASOCAINOL

Asocainol (ASOC) belongs to class I of the antiarrhytmic drugs, i.e., those that exert their action at the level of the sodium channels of t he myocardial cell membrane. It has been suggested that their molecula r mechanism of action might be through nonspecific interactions with p hospholipids that surround the channel proteins. In order to test this hypothesis, ASOC was made to interact with two multibilayer systems, one built-up of dimyristoylphosphatidylcholine (DMPC) and the other of dimyristoylphosphatidylethanolamine (DMPE). These are the type of lip ids that are respectively found in the outer and inner monolayers of h uman erythrocytes. The experiments were carried out in a hydrophobic a s well as in a hydrophilic medium below the phospholipid main transiti on temperatures. The perturbing effect of ASOC upon the bilayer struct ures was determined by X-ray diffraction. It was found that ASOC was a ble to fluidize DMPC in both media but not to DMPE.