Response of rat fasciculata-reticularis cells in primary culture to bacterial lipopolysaccharide.
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 microg/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]-Tyr23-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]-Tyr23-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 microg/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.
Enríquez de Salamanca
Amalia
A
Department of Biochemistry and Molecular Biology I, Faculty of Chemistry, Complutense University, 28040 Madrid, Spain.
García
Resurrección
R
D000324:Adrenocorticotropic Hormone / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D003345:Corticosterone / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D004926:Escherichia coli; D008070:Lipopolysaccharides / Q000302:isolation & purification / Q000378:metabolism / Q000633:toxicity*; D011284:Pregnenolone / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015385:Zona Reticularis / Q000166:cytology / Q000378:metabolism* / Q000382:microbiology*
D008070:Lipopolysaccharides; D011284:Pregnenolone; D000324:Adrenocorticotropic Hormone; D000242:Cyclic AMP; D003345:Corticosterone