Effects of beta-naphthoflavone on hepatic biotransformation and glutathione biosynthesis in largemouth bass (Micropterus salmoides).
We are investigating the effects of in vivo exposure of prototypical enzyme inducing agents on hepatic biotransformation enzyme expression in largemouth bass (Micropterus salmoides), a predatory game fish found throughout the United States and Canada. The current study targeted those genes involved in biotransformation and oxidative stress that may be regulated by Ah-receptor-dependent pathways. Exposure of bass to beta-naphthoflavone (beta-NF, 66 mg/kg, i.p.) elicited a 7-9-fold increase in hepatic microsomal cytochrome P4501A-dependent ethoxyresorufin O-deethylase (EROD) activities, but did not affect cytosolic GST catalytic activities toward 1-chloro-2,4-dinitrobenzene (CDNB) or 5-androstene-3,17-dione (ADI). Glutathione S-transferase A (GST-A) mRNA expression exhibited a transient, but non-significant increase following exposure to beta-NF, and generally tracked the minimal changes observed in GST-CDNB activities. Expression of the mRNA encoding glutamate-cysteine ligase catalytic subunit (GCLC), the rate-limiting enzyme in glutathione (GSH) biosynthesis, was increased 1.7-fold by beta-NF. Changes in GCLC mRNA expression were paralleled by increases in intracellular GSH. In summary, largemouth bass hepatic CYP1A-dependent and GSH biosynthetic pathways, and to a lesser extent GST, are responsive to exposure to beta-NF.
Hughes
Erin M
EM
Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida, P.O. Box 110885, Gainesville, FL 32611-0885, USA.
Gallagher
Evan P
EP
D000704:Analysis of Variance; D000735:Androstenedione; D000818:Animals; D001492:Bass / Q000378:metabolism*; D001711:Biotransformation / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D004137:Dinitrochlorobenzene; D004790:Enzyme Induction / Q000187:drug effects; D005721:Glutamate-Cysteine Ligase / Q000096:biosynthesis / Q000235:genetics; D005978:Glutathione / Q000378:metabolism*; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000235:genetics; D008099:Liver / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000378:metabolism*; D019324:beta-Naphthoflavone / Q000493:pharmacokinetics* / Q000633:toxicity*
D017931:DNA Primers; D018076:DNA, Complementary; D004137:Dinitrochlorobenzene; D012333:RNA, Messenger; D000735:Androstenedione; C003528:5-androstene-3,17-dione; D019324:beta-Naphthoflavone; D019363:Cytochrome P-450 CYP1A1; D005982:Glutathione Transferase; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione