Response of rat fasciculata-reticularis cells in primary culture to bacterial lipopolysaccharide

Abstract

The aim of this study was to determine the direct effect of a wide range of concentrations of lipopolysaccharide (LPS) of Escherichia coli O111:B4 on fasciculata-reticularis cells in primary cultures. In short-term cultures of fasciculata-reticularis cells, the presence of low (1–10 μg/ml) doses of LPS in the medium produced a decrease in ACTH-induced corticosterone secretion, in a dose-dependent manner and independent of the culture medium. The corticosterone production stimulated by db-cAMP was slightly decreased by the presence of LPS in culture medium, while the pregnenolone induced corticosterone biosynthesis was not modified. LPS modified the binding of [ 125I]-Tyr 23-ACTH to the fasciculata-reticularis cell membrane and the signal transduction pathway, as LPS reduced ACTH-induced cAMP production. In long-term cultures, the presence of LPS in the medium produces a decrease in the specific binding of [ 125I]-Tyr 23-ACTH, while the presence of ACTH in the culture medium produced an increase in its specific binding. The use of high doses of LPS (100–250 μg/ml) has helped to clarify some aspects of the LPS action. These doses of LPS severely inhibited ACTH-induced corticosterone production, and clearly reduced the corticosterone production stimulated by db-cAMP and the binding of ACTH to its receptors. In long-term cultures, LPS decreased the number of ACTH receptors, an effect that was reversed by subsequent exposure to ACTH. These results indicate that LPS exerts a direct action on fasciculata-reticularis cells and a model of the mechanism of LPS action is proposed.