Effect of local anesthetics on accessibility and thermal stability of the rat ovarian LH/hCG receptor

Perturbation of rat ovarian membranes induced by local anesthetics altered the accessibility and thermal stability of the LH/hCG receptor. Incubation of ovarian membranes with tetracaine and benzyl alcohol resulted in a dose-dependent loss of binding activity of the LH/hCG receptor. Possible structure-functional properties of the receptor in membranes treated with local anesthetics were analyzed by the thermal perturbation technique. The heat inactivation profile of the LH/hCG binding sites in 10 mM tetracaine and 20 mM benzyl alcohol treated membranes was shifted to lower temperatures of about 15 degrees C and 4 degrees C (T-50 values), respectively. The thermal stability of the receptor decreased with an increasing concentration of the local anesthetics. Thermal destabilization of the LH/hCG receptor induced by the action of tetracaine was higher at pH 9.5 than at pH 5.5. Treatment of ovarian membranes with 5 mM tetracaine modified and with 20 mM benzyl alcohol failed to change the quenching of protein fluorescence, characteristic for control membranes. Incubation of ovarian membranes with tetracaine and benzyl alcohol increased the membrane lipid fluidity, as determined by fluorescence polarization of the 1,6-diphenyl-1,3,5-hexatriene probe (DPH).