Inhibition of anion and glucose permeabilities by anesthetics in erythrocytes. The mechanisms of action of positively and negatively charged drugs

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1. (1) The mode of action of anesthetics as inhibitors of Cl − and glucose transports in human red cells was studied. The term anesthetic is taken in its broad meaning as defined by Seeman (Seeman, P. (1972) Pharmacol. Rev. 24, 583–655) and covers anionic and cationic liposoluble compounds which reversibly block the rising phase of the action potential, without effect on the resting membrane potential. 2. (2) Phenothiazine derivatives were chosen as prototypes of anesthetics because they represent a set of compounds having the same basic chemical structure, the phenothiazine ring, but with either a positive or a negative charge. 3. (3) The Cl − self-exchange is inhibited by both cationic and anionic derivatives. However, to obtain the same level of inhibition, it is necessary to use a concentration 10–100 times higher with cationic than with anionic drugs. 4. (4) At a concentration which inhibits Cl − permeability, cationic derivatives induce a very strong morphological change (cup-shaped cells: stomatocytes or spherostomatocytes) and protect erythrocytes against osmotic hemolysis, signifying that the membrane is fully expanded. Conversely, with anionic derivatives, inhibition occurs at a concentration which does not induce any apparent shape change or protect against osmotic hemolysis: there is no significant membrane expansion. 5. (5) Glucose permeability, measured by glucose exit, is inhibited by cationic and anionic phenothiazine, but always at a concentration which fully expands the membrane as indicated by morphological changes and anti-hemolytic effects. It is interesting to point out that whilst glucose exit shows inhibition by cationic derivatives, glucose exchange flux is scarcely altered. 6. (6) It is concluded that cationic and anionic anesthetics are general inhibitors of transmembrane solute movements involving a facilitated-diffusion process. However, the mechanism of inhibition of glucose permeability by anionic and cationic anesthetics, as well as inhibition of Cl − permeability by cationic anesthetics may be of a non-specific nature and result from their interaction with the bilayer (this indirect effect is discussed); on the other hand, inhibition of Cl − permeability by anionic anesthetics may result from a specific perturbation of the transport mechanism according to recent evidence in some cases (Cousin, J.L. and Motais, R. (1979) J. Membrane Biol. 46, 125–153; Zaki, L., Ruffing, W., Gärtner, E.M., Fasold, H., Motais, R. and Passow, H. (1977) 11th FEBS Meeting, Copenhagen, A4 17–671.