Regulation of mouse P(1)450 gene expression in monolayer-cultured hepatocytes from responsive and non-responsive strains.
Regulation of P(1)450 gene expression in mouse hepatocytes from responsive (C57BL/6) and non-responsive (DBA/2) strains in primary culture was investigated with respect to aryl hydrocarbon hydroxylase (AHH) activity and P450 transcript levels. Although significant induction of AHH activity in C57BL/6 mouse hepatocytes after exposure to benz[aanthracene (BA) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was observed 24 h after the beginning of cultivation, the response was more prominent after longer periods. AHH induction in DBA/2 mouse hepatocytes by TCDD was also evident after 24 h treatment, but that by BA was delayed, only becoming significant after 3 days. Limited treatment with cycloheximide (CHI) for the initial 8 h affected AHH activity measured after 24 h; BA-induced AHH activity was decreased if the treatment started day 1 after seeding of the cells from either strain, whereas if started at day 3 the enzyme activities in hepatocytes from C57BL/6 strain were approximately doubled and those from DBA/2 increased to 130%. Treatment with dibutyryl cAMP or forskolin, a specific activator for adenyl cyclase, increased BA-induced AHH activities. 3-Methoxybenzamide, a specific inhibitor of poly(ADP-ribose) polymerase, significantly increased both basal and BA-induced AHH activities of hepatocytes from both strains at days 3 and 5, reduction of P(1)450 transcripts also being evident in the latter case. The observations indicate qualitatively similar but quantitatively different regulation of AHH induction in both responsive and non-responsive mouse strains. Furthermore the regulation changed with increasing cultivation period. Previously described regulation mechanisms in cultured cells were observed to operate a few days after seeding, possibly after adaptation of hepatocytes to the culture conditions.
Nemoto
N
N
Department of Experimental Pathology, Cancer Institute, Tokyo, Japan.
Sakurai
J
J
Tazawa
A
A
Ishikawa
T
T
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis; D001551:Benz(a)Anthracenes / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D051379:Mice; D008815:Mice, Inbred Strains; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D014158:Transcription, Genetic
D001551:Benz(a)Anthracenes; D001549:Benzamides; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D000072317:Polychlorinated Dibenzodioxins; D003994:Bucladesine; D003513:Cycloheximide; D000242:Cyclic AMP; D001189:Aryl Hydrocarbon Hydroxylases; C025159:3-methoxybenzamide