N. Selim et al., Differential lobular induction in rat liver of glutathione S-transferase A1/A2 by phenobarbital, AM J P-GAST, 278(4), 2000, pp. G542-G550
Citations number
30
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
Phenobarbital and other xenobiotics induce drug-metabolizing enzymes, inclu
ding glutathione S-transferase A1/A2 (rGSTA1/A2). We examined the mechanism
of induction of rGSTA1/A2 in rat livers after phenobarbital treatment. The
induction of rGSTA1/A2 was not uniform across the hepatic lobule; steady-s
tate transcript levels were threefold higher in perivenous hepatocytes rela
tive to periportal hepatocytes when examined by in situ hybridization 12 h
after a single dose of phenobarbital. Administration of a second dose of ph
enobarbital 12 or 24 h after the first dose did not equalize the induction
of rGSTA1/A2 across the lobule. The transcriptional activity of the rGSTA1/
A2 gene was increased 3.5- to 5.5-fold in whole liver by phenobarbital, but
activities were the same in enriched periportal and perivenous subpopulati
ons of hepatocytes from phenobarbital-treated animals. The half-life of rGS
TA1/A2 mRNA in control animals was 3.6 h, whereas it was 10.2 h in phenobar
bital-treated animals. We conclude that phenobarbital induces rGSTA1/A2 exp
ression by increasing transcriptional activity across the lobule but induct
ion of rGSTA1/A2 is greater in perivenous hepatocytes due to localized stab
ilization of mRNA transcripts.