Membrane-buffer partition coefficients of a local anesthetic tetracaine monitored by an anesthetic sensor; effects of temperature and pH

Abstract

Binding of a local anesthetic tetracaine (TC) to dimyristoylphosphatidylcholine (DMPC) bilayer membrane was studied by the potentiomerty with an ion-selective electrode sensitive to TC cation. DMPC membrane-buffer partition coefficient ( K app) was determined in mole fraction unit as a function of pH for the lamellar gel (at 12°C), ripple gel (at 20°C), and liquid crystal (at 30°C) phases. The partition coefficients of charged ( K +) and uncharged TC ( K 0) into the DMPC membranes were estimated from the pH-dependence of K app. The three states of DMPC membranes were more receptive to the uncharged TC than the charged species.