Mapping of phenytoin-inducible cytochrome P450 immunoreactivity in the mouse central nervous system.

The distribution of phenytoin-inducible cytochrome P450 in non-treated mouse brain and spinal cord was analysed immunohistochemically using polyclonal antibodies against phenytoin-induced mouse cerebral microsomal P450. This P450 protein was proved in Ouchterlony [Volk B. et al.

Comparison of enzyme phenotypes in human bladder tumours and experimentally induced hyperplastic and neoplastic lesions of the rat urinary bladder. A combined histochemical and immunohistochemical approach.

The expression of a number of enzymes involved in drug metabolism, membrane function etc. was compared in hyperplastic and neoplastic lesions of the rat bladder and in human bladder tumours. Transitional cell carcinomas (TCC) in both rat and Man were characterized by decreased alkaline phosphatase (ALP) and increased gamma-glutamyl transpeptidase (GGT), beta-glucuronidase (beta-G1), succinate dehydrogenase (SD) and glucose-6-phosphate dehydrogenase (G6PD) activities.

Effect of nutritional imbalances on cytochrome P-450 isozymes in rat liver.

Male Sprague-Dawley rats were fed for six weeks either a control diet containing 22% casein (C) and 5% fat (F) or a low-protein diet (6% C, 5% F) or high-lipid diet (30% C, 30% F). A group of rats received a control diet containing 50 ppm of Phenoclor DP6. Three major forms of cytochrome P-450, UT 50, BP 3a and MC 2 were purified from livers of DP6-fed rats and only two forms, UT 50 and PB 3a, were purified from control and dietary groups.

Effect of modifying agents on the phenotypic expression of cytochrome P-450, glutathione S-transferase molecular forms, microsomal epoxide hydrolase, glucose-6-phosphate dehydrogenase and gamma-glutamyltranspeptidase in rat liver preneoplastic lesions.

The expression of A and P forms of glutathione S-transferase (GST-A and P), two cytochrome P-450 isoenzymes (P-450 PB3a and P-450 MC2), microsomal epoxide hydrolase (mEHb), glucose-6-phosphate dehydrogenase (G6PD) and gamma-glutamyltranspeptidase (gamma-GT) was compared in preneoplastic liver lesions and background parenchyma of F344 rats post-treated with butylated hydroxyanisole (BHA), ethoxyquin (EQ) or acetaminophen (AAP). These latter three compounds have been shown to inhibit hepatocarcinogenesis after initial treatment with N-ethyl-N-hydroxyethylnitrosamine (EHEN) and a significant decrease in the number of enzyme-altered foci and nodules positive for GST-P, GST-A, G6PD and gamma-GT and negative for P-450 PB3a, P-450 MC2 was associated with their administration. Whereas in the foci case the decrease was most prominent for non-discrete (heterogeneous) type lesions, the results of quantitation of nodules revealed a most significant alteration in the discrete homogeneously staining population.

First evidence of cytochrome P-450 induction in the mouse brain by phenytoin.

Long-term administration of phenytoin (60 mg/kg) to male C57Bl/6J mice causes an average drug serum level of 16-19 micrograms/ml. Cytological changes consisting of focal axonal swellings in the deep cerebellar nuclei are characterized by an increasing accumulation of vesiculotubular membranes in the dense, but ribosome-deficient axoplasm. Microsomal fractions of brain and liver were prepared at intervals until the 80th day of treatment to determine their cytochrome P-450 activities and isoenzyme characteristics.

Effect of antibodies against cytochrome P-450 on demethylation and denitrosation of N-nitrosodimethylamine and N-nitrosomethylaniline.

Rat liver microsomes which were induced either with ethanol or PB were incubated with NDMA or NMA. Formaldehyde generation and nitrite formation were measured as metabolic parameters for oxidative bioactivation and denitrosation, respectively. The influence of antiserum PB3a1 and PB22 containing antibodies against the corresponding cytochrome P-450 species on both metabolic functions was investigated.

Effect of unbalanced diets on incorporation of delta-aminolevulinic acid into cytochrome P-450.

The in vivo syntheses of two liver microsomal cytochromes P-450 PB3a, P-450 UT50 [(1987) Eur. J. Biochem.

Altered drug metabolizing potential of acinar cell lesions induced in rat pancreas by hydroxyaminoquinoline 1-oxide.

Foci of atypical acinar cells observed in male rats 1 year after a single injection of hydroxyaminoquinoline 1-oxide (HAQO) were assessed immunohistochemically for altered expression of a number of enzyme forms considered to play important roles in drug metabolism. The pancreatic lesions, classified as of either basophilic or eosinophilic type on histological appearance, demonstrated distinctive patterns of altered enzyme phenotype. On the one hand, the basophilic foci composed of enlarged cells/nuclei with very prominent nucleoli were characterized by increase in GST-P, G6PD and P450 PB1 and MC2 forms.

The effect of dietary imbalances on the activation of benzo[a]pyrene by the metabolizing enzymes from rat liver.

Male Sprague-Dawley rats (70-80 g) were fed ad libitum a standard control diet (22% casein, 5% lard), or a high lipid diet (30% lard) or a low protein diet (6% casein) or a standard diet containing 50 ppm phenoclor DP6. After 6 weeks on these diets, the cytochrome P-450 microsomal content, the benzo[a]pyrene monooxygenase (BaP-MO) and the epoxide hydrolase (EH) were assayed. The formation of mutagenic B(a)P metabolites which covalently bind with DNA was compared.

Immunohistochemically demonstrated altered expression of cytochrome P-450 molecular forms and epoxide hydrolase in N-ethyl-N-hydroxyethylnitrosamine-induced rat kidney and liver lesions.

A comparison of N-ethyl-N-hydroxyethylnistrosamine (EHEN)-induced preneoplastic and neoplastic lesions in the rat liver and kidney was made with respect to the expression of different drug metabolizing enzymes. Four cytochrome P-450 species (cyt. P-450 UT50, PB3a, MC1 and MC2) and microsomal epoxide hydrolase (mEHb) were investigated along with two glutathione S-transferase species (GST-P and A forms) earlier shown to be elevated in putative preneoplastic lesions in the liver and kidney, respectively.

Isoenzyme-specific phosphorylation of cytochromes P-450 and other drug metabolizing enzymes.

A series of fourteen cytochrome P-450 isoenzymes was treated with three different protein kinases and found to divide into isoenzymes phosphorylated by both the cyclic AMP-dependent kinase and the calcium-phospholipid-dependent kinase (P-450 PB 3a and PB 2e), by none of these kinases (P-450 PB 1b, MC 1b, UT 1, and thromboxane synthase), and by either the cyclic AMP-dependent kinase (P-450 LM 2, PB 2d, and PB 3b) or the calcium-phospholipid-dependent kinase (P-450 PB 1a, PB 2a, MC 1a, LM 3c, and LM 4). Other components of the monooxygenase system, cytochrome P-450 reductase, cytochrome b5, cytochrome b5 reductase as well as microsomal epoxide hydrolase, were poor substrates for the kinases employed. On the other hand, glutathione transferases 1-2 and 4-4, but not 3-3, were relatively good substrates for the calcium-phospholipid-dependent kinase.

Identification of human cytochromes P-450 analogous to forms induced by phenobarbital and 3-methylcholanthrene in the rat.

Antibodies to four rat liver forms of cytochrome P-450, two phenobarbital-inducible (PB1 and PB2) and two 3-methylcholanthrene-inducible (MC1 and MC2) proteins, have been used to make a structural and functional comparison of rat and human cytochromes P-450. Proteins from both species were identified on Western blots by their reaction with these antibodies. In the human liver preparations, structurally related proteins to PB1 and to PB2 were identified in all the samples tested with apparent Mr values of 51 800 and 54 800 for PB1 and 53 600 and 57 200 for PB2.