Abstract

Human erythrocyte membranes at pH 7.4 in 310 imosm sodium phosphate buffer show severa1 distinct endothermic transitions when studied by differential heat capacity calorimetry. Various tranquilizers in the phenothiazine family shift one of these major transitions, normally at 67°, down to about 60° when present at concentrations of the order of 40 µM or less. The lower aliphatic alcohols in dilute concentrations affect two of these transitions and at higher concentrations shift all the transitions down, by temperatures as much as 30°. The concentrations of alcohols needed to cause similar effects decrease with increasing number of carbon atoms. The effect of alcohols and phenothiazines below 150 µM can be reversed by washing the membranes in sodium phosphate buffer. The common effect of all these compounds at anesthetic concentrations seems to be mainly on one transition, which has been tentatively identified as involving a lipid domain on the membrane which has previously been shown to function in anion transport.