ABSTRACT
The detergents, alkyltrimethylammonium bromide, N-alkyl-N, N-dimethyl-3-ammonio-1-propanesulfonate (zwittergent), alkane sulfonate, alkylsulfate, alkyl-beta-D-glucopyranoside, alkyl-beta-D-maltoside, dodecanoyl-N-methylglucamide, polyethylene glycol monoalkyl ether and Triton X-100, all produce a concentration-dependent acceleration of the slow passive transbilayer movement of NBD-labeled phosphatidylcholine in the human erythrocyte membrane. Above a threshold concentration, which was well below the CMC and characteristic for each detergent, the flip rate increases exponentially upon an increase of the detergent concentration in the medium. The detergent-induced flip correlates with reported membrane-expanding effects of the detergents at antihemolytic concentrations. From the dependence of the detergent concentration required for a defined flip acceleration on the estimated membrane volume, membrane/water partition coefficients for the detergents could be determined and effective detergent concentrations in the membrane calculated. The effective membrane concentrations are similar for most types of detergents but are 10-fold lower for octaethylene glycol monoalkyl ether and Triton X-100. The effectiveness of a given type of detergent is rather independent of its alkyl chain length. Since detergents do not reduce the high temperature dependence of the flip process the detergent-induced flip is proposed to be due to an enhanced probability of formation of transient hydrophobic structural defects in the membrane barrier which may result from perturbation of the interfacial region of the bilayer by inserted detergent molecules.
Subject(s)
Detergents/chemistry , Erythrocyte Membrane/chemistry , Phospholipids/chemistry , 4-Chloro-7-nitrobenzofurazan , Humans , Hydrogen-Ion Concentration , Indicators and Reagents , Lauric Acids/chemistry , Solubility , Water/chemistryABSTRACT
The combined effect of preliminary dehydration of erythrocytes and the cationic amphiphilic compound, chlorpromazine, on the stability of cells to subsequent hyperosmotic effect, has been studied. A protective effect of chlorpromazine depending on the degree of initial cell dehydration and temperature was found. The results obtained by an addition of the cationic amphiphile at preliminary stages of the experiment and directly in the process of development of hyperosmotic lysis have been compared. A conclusion was drawn that the observed effect is not due to preliminary treatment of cells with chlorpromazine and is therefore unrelated to its influence on the regulatory systems of the cell. It has been shown also that under cold shock conditions the earlier established protective effect of chlorpromazine is also directly realized at the moment of stress exposure, i.e., with a change in temperature.
