Hydroxylation, sulfation, and conjugation of bile acids in rat hepatoma and hepatocyte cultures under the influence of glucocorticoids
We have studied the effect of a glucocorticoid on bile acid metabolism in three monolayer systems: 1) rat hepatoma Faza 967, 2) primary cultures of rat fetal liver, 3) short term cultures of adult rat hepatocytes. In System 1, dexamethasone increases tauroconjugation of the dihydroxylated acids, induces reversibly the conjugation of cholate, the synthesis of deoxycholate 3-monosulfate from deoxycholic acid, the hydroxylation of deoxycholate in the 6β and 7α positions, the hydroxylation of taurodeoxycholate, and, most actively, the 6β-hydroxylation of chenodeoxycholate and taurochenodeoxycholate. The hydroxylation of the two dihydroxylated acids does not seem to require prior conjugation to taurine, nor does its induction proceed as a consequence of enhanced tauroconjugation. The effect of dexamethasone on 6β-hydroxylation is inhibited by cycloheximide. Corticosterone also induces the hydroxylation and the monosulfate synthesis. 3-Methylcholanthrene, benzo(a)anthracene, and phenobarbital do not induce chenodeoxycholate hydroxylation. In System 2, dexamethasone increases and maintains tauroconjugation and hydroxylation. In System 3, both control and dexamethasone-treated groups conjugate bile acids to taurine and glycine and hydroxylate actively the dihydroxylated acids for about 72 h. The distribution of these differentiation criteria was also studied among four closely related hepatoma lines: (a) a differentiated clone, (b) a dedifferentiated variant, (c) a cell hybrid obtained by crossing a and b, exhibiting extinction of hepatic functions, and (d) a segregated subclone of c that re-expresses all these functions. It was the same as that of other liver-specific traits, and most of the liver functions, when present, were expressed together. The glucocorticoid induction of a cytochrome P-450-mediated monooxygenase activity in cultured cells has in vivo implications and might contribute to the development of a sensitive and versatile pharmacological screening system.