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

Binding of a local anesthetic tetracaine (TC) to dimyristoylphosphatidylcho line (DMPC) bilayer membrane was studied by the potentiomerty with an ion-s elective electrode sensitive to TC cation. DMPC membrane-buffer partition c oefficient (K-app) was determined in mole fraction unit as a function of pH for the lamellar gel (at 12 degrees C), ripple gel (at 20 degrees C), and liquid crystal (at 30 degrees C) phases. The partition coefficients of char ged (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 r eceptive to the uncharged TC than the charged species. (C) 1998 Elsevier Sc ience Ireland Ltd. All rights reserved.