Implication of membrane functions in toxicology.

The following are defined: the structural and biochemical characteristics of the membrane constituents involved in the functional activity; the importance of the environment of the proteins in the expression of their activity; and the adaptation possibilities of the membrane's functions to the nutritional distortions or to the action of drugs. The membrane's functions, as a hydrophobic barrier and its essential activities, are analysed in relation to their involvement in toxicology with examples of substances having a great specificity of action. On the other hand, the case of substances impairing, in a non-specific way, the membrane's functional state, very frequently the case in food toxicology, is analysed through the modification of the hydrophobic interaction forces that they induce. Two membranes playing a key role in food toxicology are especially studied: the enterocyte brush border, of which the essential function is absorption and which represents the first barrier to the component brought by food; and the smooth endoplasmic reticulum, which counts among its essential functions the detoxication of xenobiotics and the control of cytoplasmic Ca2+ concentration. The consequences on these functions of a change of the membrane's molecular interaction forces under the in vitro action of a series of substances having different lipophilic power (n-aliphatic alcohols, N-phenyl carbamates, methoxybenzene derivatives) are presented. The consequences of nutritional distortions (ethanol administration or diets deficient in essential fatty acids) on the in vivo adaptation of these membranes under conditions which also modify the membrane interaction forces are also considered.