GLUCOCORTICOID-DEPENDENT INDUCTION OF THE MESSENGER-RNA CODING FOR ARGININOSUCCINATE LYASE IN CULTURED FETAL-RAT HEPATOCYTES

Dexamethasone increased both argininosuccinate lyase (ASL) activity an d specific mRNA level in cultured fetal hepatocytes. Addition of vario us inhibitors of RNA synthesis showed that the increase in ASL mRNA ma y be related to an enhancement of ASL gene transcription, but not to a specific messenger stabilization. An apparent half-life of about 12 h for ASL mRNA was found in both untreated and dexamethasone-treated he patocytes. About 30 h were necessary to observe the maximal effect of dexamethasone, and, in addition, both puromycin and cycloheximide (two inhibitors of protein synthesis) blocked the inducing effect of the s teroid. These results suggested the involvement of intermediary protei n(s) in the mechanism of induction of ASL mRNA by glucocorticoids.