Characterization of hepatic cytochrome P450 isozyme composition in the transgenic rat expressing low level human growth hormone.
1. The present authors have previously developed a transgenic rat carrying a chimeric gene of the mouse whey acidic protein promoter and the structural portion of human growth hormone (GH) gene. Among this (hGH-TG) rat, a line (low GH rat) missing a male-specific pulsatile GH secretary pattern due to suppression of endogenous GH secretion and having a continuous low GH (hGH and rat GH) level in the peripheral circulation was identified. The latter rat was also characterized as having severe obesity with age. This strain (low Gh rat) was used to correlate the sex-specific secretory pattern of GH with the sex-specific expression of cytochrome P450 (CYP) in rat. 2. Comparisons were made between the low GH rat and the non-transgenic rat as to the expression of liver microsomal CYP isozymes. The following enzyme activities were assessed: testosterone (T) hydroxylation and oxidation; ethoxyresorufin O-dealkylation (EROD); bunitrolol (BTL) 4-hydroxylation and T5 alpha-reduction. Protein expression of CYP1A, CYP2C11, CYP2D, CYP2E1, CYP3A2 and CYP4A1 were also assessed by Western blot analysis. 3. Enzyme activities and protein expression of CYP2C11 (T16 alpha and 2alpha-hydroxylase and 17-oxidase activities) and CYP3A2 (T6beta and 2beta-hydroxylase activities) levels, which are known to be higher in the male than in the female rat, were significantly lower in the adult male low GH rat than in the control male rat. In contrast, CYP2A1 (T7 alpha-hydroxylase) and T5-alpha-reductase activities, which are known to be specifically elevated in the female, were significantly higher in the adult male low GH rat than in the control male rat. Thus, the loss of male-specific secretory pattern of GH results in feminization of the pattern of expression of CYP and T5 alpha-reductase activity in the liver. 4. In contrast to other GH-deficient models so far studied, an increase in CYP4A1 and a decrease in CYP2E1 protein expression were observed in the low GH rat. These trends are consistent with the characteristic phenotype of obesity in the transgenic rat because CYP4A1 and CYP2E1 enhance fatty acid excretion and glyconeogenesis from fatty acids respectively.
Takahashi
J
J
Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Furuhata
Y
Y
Ikeda
A
A
Takahashi
M
M
Iwata
H
H
Kazusaka
A
A
Fujita
S
S
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D030801:Animals, Genetically Modified; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D042926:Cytochrome P-450 CYP4A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D000072467:Cytochrome P450 Family 2; D004195:Disease Models, Animal; D005260:Female; D019382:Human Growth Hormone / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008658:Inactivation, Metabolic; D007527:Isoenzymes / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012737:Sex Factors; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000378:metabolism
D007527:Isoenzymes; D008565:Membrane Proteins; D019382:Human Growth Hormone; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D013250:Steroid Hydroxylases; D019392:Cytochrome P-450 CYP2E1; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; C465260:Cyp3a2 protein, rat; D019363:Cytochrome P-450 CYP1A1; D051544:Cytochrome P-450 CYP3A; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; C022657:steroid hormone 6-beta-hydroxylase; D042926:Cytochrome P-450 CYP4A; C071864:bunitrolol 4-hydroxylase; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase