Divergent Regulation of the Class II P-Glycoprotein Gene in Primary Cultures of Hepatocytes versus H35 Hepatoma by Glucocorticoids’

We investigated whether the glucocorticoid-mediated mechanisms controlling P-glycoprotein (pgp2 or mdrl b) are similar in normal hepatocytes compared with the H35 hepatoma cell line. In primary rat hepatocytes, dexamethasone (DEX) caused a dose- and time-dependent decrease in the amount of the pgp2 mRNA, which correlated with fundional pgp2 expression (intracellular accumulation of [3H]vincristine). The suppression of pgp2 mRNA was specific for glucocorticoids because a representative estrogen and progestin were without effed, and DEX suppression of pgp2 mRNA could be reversed by cotreatment with an anti-glucocorticoid. DEX suppression of pgp2 mRNA appears to be posttranscriptional because followin