Influence of E. coli endotoxin on ACTH induced adrenal cell steroidogenesis

The effect of endotoxin (lipopolysaccharide from E. coli) on isolated adrenocortical cells was examined. Lipopolysaccharide decreased the ACTH-induced steroidogenesis. This effect was shown by all corticotropin concentrations studied, and the longer the incubation time, the higher the effect produced. The rate of decrease of ACTH-induced steroidogenesis was dependent on the concentration of lipopolysaccharide in the medium. Binding of [125I]ACTH to adrenocortical cells was modified by lipopolysaccharide; this modification was related to a decrease of the ACTH-induced steroidogenesis. This effect supports the hypothesis of a direct interaction between lipopolysaccharide and the cell membrane with a concomitant distortion of the cell surface affecting the ACTH receptor sites of their environment. [14C]Lipopolysaccharide binds to isolated adrenocortical cells. Binding specificity was investigated by competitive experiments in the presence of various types of endotoxins, polypeptide hormones and proteins. Unlabelled lipopolysaccharide from the same bacterial strain and isolated under identical conditions than the labelled lipopolysaccharide exerted the strongest inhibitory activity. Unlabelled lipopolysaccharide of various strains different from that originating the labelled lipopolysaccharide exerted the less displacement. It would imply a certain kind of specificity but the decrease in the binding of lipopolysaccharide produced by ACTH and glucagon suggests the existence of non-specific interactions between lipopolysaccharide and cell membrane.