Propranolol, chlorpromazine and platelet membrane: a fluorescence study of the drug-membrane interaction

The binding of propranolol 1 μM (PRO) and chlorpromazine 35 μM (CPZ) was studied on liposomes of the main platelet phospholipids: phosphatidylcholine (PC), phosphatidylethanolamine (PE) phosphatidylserine (PS), phosphatidylinositol (PI) and sphingomyelin (SPH), on the pool of platelet extracted phospholipids (PPL) and on platelet membrane (PM) by means of the fluorescence emission properties of the two drugs. We concluded that PRO and CPZ bind preferentially with PS and PI which are localized in the inner bilayer of the platelet membrane. This result is the first experimental evidence of the suggestion of many authors that cationic drugs bind to negative phospholipids.