Expression, microsomal and mitochondrial activities of cytochrome P450 enzymes in brain regions from control and phenobarbital-treated rabbits.
Expression and monooxygenase activity of various cytochrome P450 (CYP) enzymes along with constitutive androstane (CAR) and the pregnane X (PXR) receptors were investigated in the brain of control and phenobarbital-treated rabbits (80 mg/kg for 4 days). RT-PCR analysis, using specific primers, demonstrated that in control rabbits mRNAs of CYP 2A10, 2B4/5 and 3A6 were expressed, though to a different extent, in the liver, as well as in brain cortex, midbrain, cerebellum, striatum, hippocampus and hypothalamus, whilst CYP2A11 and 4B1 were not expressed in the hypothalamus. CAR was expressed in liver and all the brain regions examined, whereas the PXR was expressed only in liver and cortex. Real time RT-PCR analysis demonstrated that in vivo treatment with phenobarbital, in contrast with what happened in liver, did not induce the expression of CYP 2B4/5 mRNA in cortex, midbrain and cerebellum. NADPH cytochrome c reductase and some other enzymatic activities markers of CYP 2A, 2B, 3A and 4B activities were studied in liver microsomes as well as in microsomes and mitochondria of brain cortex, midbrain and cerebellum of control and phenobarbital-treated rabbits. In contrast to what was observed in liver, phenobarbital treatment did not induce the aforementioned monooxygenase activities in brain. However, we cannot exclude that a longer phenobarbital treatment may lead to a significant induction of CYP activities in brain. These findings indicated that brain CYPs, despite the presence of CAR, were resistant to phenobarbital induction, indicating a possible different regulation of these enzymes between brain and liver.
Marini
Sandra
S
Istituto di Fisiologia Clinica, Area della Ricerca CNR, via Moruzzi 1, 56100, Pisa, Italy.
Nannelli
Annalisa
A
Sodini
Daria
D
Dragoni
Stefania
S
Valoti
Massimo
M
Longo
Vincenzo
V
Gervasi
Pier Giovanni
PG
D000731:Androstanes / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D015415:Biomarkers; D001921:Brain / Q000201:enzymology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D018076:DNA, Complementary / Q000032:analysis / Q000096:biosynthesis; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008861:Microsomes / Q000201:enzymology*; D008928:Mitochondria / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D008969:Molecular Sequence Data; D010634:Phenobarbital / Q000494:pharmacology*; D000077297:Pregnane X Receptor; D012313:RNA / Q000032:analysis / Q000096:biosynthesis; D011817:Rabbits; D011987:Receptors, Steroid / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000731:Androstanes; D015415:Biomarkers; D018076:DNA, Complementary; D006993:Hypnotics and Sedatives; D007527:Isoenzymes; D000077297:Pregnane X Receptor; D011987:Receptors, Steroid; D012313:RNA; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C033936:androstane; D010634:Phenobarbital