Glucocorticoid regulation of polycyclic aromatic hydrocarbon induction of cytochrome P450IA1, glutathione S-transferases, and NAD(P)H:quinone oxidoreductase in cultured fetal rat hepatocytes.
The regulation of polycyclic aromatic hydrocarbon-inducible enzymes, cytochrome P450IA1, NAD(P)H:quinone oxidoreductase, and glutathione S-transferases, by glucocorticoids was investigated using primary fetal rat hepatocyte culture. Treatment of cells in culture with 1,2-benzanthracene (100 microM, 72 hr) resulted in 60-, 2-, and 6-fold increases in cytochrome P450IA1, glutathione S-transferase, and NAD(P)H:quinone reductase activities, respectively. The inductive effect of 1,2-benzanthracene on cytochrome P450IA1 and glutathione S-transferase (1-chloro-2,4-dinitrobenzene conjugation) activities was potentiated approximately 3- and 2- to 3-fold, respectively, when dexamethasone (0.01-1 microM) was included in the culture medium. In contrast, 1 microM dexamethasone was found not to potentiate the induction of NAD(P)H:quinone oxidoreductase activity by 1,2-benzanthracene. Treatment of cultured hepatocytes with dexamethasone alone, at concentrations of up to 100 microM, resulted in a 2- to 4-fold increase in glutathione S-transferase and NAD(P)H:quinone oxidoreductase activity. Both the induction of glutathione S-transferase activity by high concentrations of dexamethasone alone and the potentiation of 1,2-benzanthracene induction by lower concentrations of dexamethasone were observed for other steroids of the glucocorticoid class in conjunction with a variety of polycyclic aromatic hydrocarbons. Western immunoblot analyses indicated that low concentrations of dexamethasone (0.1-1 microM) potentiated 1,2-benzanthracene-dependent induction of cytochrome P450IA1, glutathione S-transferase Ya/Yc subunit and NAD(P)H:quinone oxidoreductase content. Additionally, increased glutathione S-transferase activity in response to concentrations of dexamethasone exceeding 1 microM was associated with concomitant increases in Ya/Yc and Yb subunit content. Potentiation of polycyclic aromatic hydrocarbon induction of cytochrome P450IA1, glutathione S-transferase, and NAD(P)H:quinone oxidoreductase protein content by low concentrations of glucocorticoids and induction of glutathione S-transferase and NAD(P)H:quinone oxidoreductase by high concentrations of glucocorticoids alone indicates the importance of these endogenous compounds in the regulation of some hepatic enzymes involved in xenobiotic metabolism.
Sherratt
A J
AJ
Department of Biochemistry, University of Louisville, School of Medicine, KY 40292.
Banet
D E
DE
Prough
R A
RA
D000818:Animals; D001551:Benz(a)Anthracenes / Q000494:pharmacology; D015153:Blotting, Western; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D003907:Dexamethasone / Q000494:pharmacology; D004357:Drug Synergism; D004790:Enzyme Induction / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D005982:Glutathione Transferase / Q000096:biosynthesis*; D008099:Liver / Q000187:drug effects* / Q000196:embryology / Q000201:enzymology; D011083:Polycyclic Compounds / Q000494:pharmacology*; D011808:Quinone Reductases / Q000096:biosynthesis*; D051381:Rats; D011919:Rats, Inbred Strains
D001551:Benz(a)Anthracenes; D005938:Glucocorticoids; D011083:Polycyclic Compounds; D003907:Dexamethasone; D003577:Cytochrome P-450 Enzyme System; C030935:benz(a)anthracene; C041831:NADH dehydrogenase (quinone); D011808:Quinone Reductases; D005982:Glutathione Transferase