INDIRECT DEXAMETHASONE DOWN-REGULATION OF THE LIVER FATTY-ACID-BINDING PROTEIN EXPRESSION IN RAT-LIVER

The effects of glucocorticoids on the regulation of the liver fatty ac id-binding protein (L-FABP) were studied in vivo and in primary cultur e of hepatocytes in rats. No change in L-FABP cytosolic content and mR NA levels occurred after adrenalectomy. By contrast, a twofold decreas e in L-FABP expression was found in dexamethasone (Dex) treated rats. In primary culture of rat hepatocytes, insulin did not modify the L-FA BP mRNA levels, whereas Dex produced a significant decrease. This down -regulation was independent of specific glucocorticoid receptors, of a lteration in the turnover of L-FABP mRNA and did not require a de novo protein synthesis. However, it was totally pretended when 320 mu M ol eic acid was added in the culture medium. These findings show that the dex-mediated down-regulation of the L-FABP expression found in vivo i s not due to a direct endocrine effect, but is likely secondary to cha nges in cellular lipid metabolism. (C) 1998 Elsevier Science B.V.