Induction of gamma-glutamyl transferase by dexamethasone in cultured fetal rat hepatocytes.
Hepatocytes isolated as a relatively pure population from normal fetal rats were maintained in primary monolayer culture for 4-10 days. Hepatocytes exhibited a small increase in basal gamma-glutamyl transferase (GGT) activity over time. Exposure to dexamethasone (10(-6) mol/l) elicited a rise in GGT activity after a lag of 24 h. The presence of the steroid was necessary to maintain induction, and its removal resulted in reversal of induction. The maximal response was 2- to 3-fold, 72 h after exposure to the steroid. After this maximal response, a gradual decay in enzyme activity occurred, despite the continuous presence of the hormone. Actinomycin D or cycloheximide given prior to/or simultaneously with the steroid prevented the induction, thus suggesting that both RNA and protein biosynthesis are necessary for induction to occur.
Cotariu
D
D
Institute of Biochemical Pathology, Assaf Harofeh Medical Center, Tel Aviv, Israel.
Barr-Nea
L
L
Papo
N
N
Zaidman
J L
JL
D000818:Animals; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003561:Cytarabine / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D004790:Enzyme Induction; D005333:Fetus; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000196:embryology / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D005723:gamma-Glutamyltransferase / Q000096:biosynthesis*
D003561:Cytarabine; D003609:Dactinomycin; D003907:Dexamethasone; D003513:Cycloheximide; D005723:gamma-Glutamyltransferase