scholarly journals High activity of cytochrome P-450-linked aminopyrine N-demethylase in mouse brain microsomes, and associated sex-related difference

1989 ◽  
Vol 261 (3) ◽  
pp. 769-773 ◽  
Author(s):  
V Ravindranath ◽  
H K Ananda Theertha Varada
Keyword(s):  
Mouse Brain ◽  
Male Mouse ◽  
Mouse Liver ◽  
Double Diffusion ◽  
Microsomal Protein ◽  
Cross Reactivity ◽  
Related Difference ◽  
Brain Microsomes ◽  
Demethylase Activity ◽  
Cytochrome P 450

The presence of cytochrome P-450 and associated mono-oxygenase activities was examined in brain microsomes from male and female mice. Although the cytochrome P-450 level in male mouse brain was very low as compared with mouse liver, the aminopyrine N-demethylase and morphine N-demethylase specific activities in male mouse brain were much higher than those observed in mouse liver. Ethoxycoumarin O-de-ethylase and aniline hydroxylase activities were, however, not detected in mouse brain. Sex-related differences were observed in both the cytochrome P-450 levels and aminopyrine N-demethylase activity in mouse brain, the levels of both being higher in male mouse brain as compared with female mouse brain. Aminopyrine N-demethylase activity in mouse brain microsomes was dependent on the presence of oxygen and NADPH and could be inhibited by piperonyl butoxide, N-octyl imidazole and carbon monoxide. Antiserum raised to the phenobarbital-inducible form of rat liver cytochrome P-450 [P-450(b+e)] inhibited mouse brain aminopyrine N-demethylase activity by around 80+ mouse brain microsomal protein exhibited cross-reactivity against this antiserum when examined by Ouchterlony double diffusion and immunoblotting. The present results indicate the presence of a phenobarbital-inducible form of cytochrome P-450 (or a form of cytochrome P-450 that is similar immunologically) in mouse brain microsomes, which is associated with a sex-related difference.

Cytochrome P-450 and hepatic drug biotransformation during progressive cardiac disease in cardiomyopathic hamsters

1979 ◽  
Vol 57 (3) ◽  
pp. 302-304 ◽  
Author(s):  
Kenneth W. Renton ◽  
James C. Baker ◽  
Leslie E. Bailey
Keyword(s):  
Heart Failure ◽  
Cardiac Disease ◽  
Disease Process ◽  
Microsomal Protein ◽  
Hepatic Drug ◽  
Drug Biotransformation ◽  
Hepatic Microsomes ◽  
Cardiomyopathic Hamsters ◽  
Demethylase Activity ◽  
Cytochrome P 450

Reductions in cytochrome P-450 levels and aminopyrine N-demethylase activity of hepatic microsomes obtained from cardiomyopathic hamsters (BIO 14.6) occurred at all stages of the disease before the development of congestive heart failure (CHF). Cytochrome b5 levels were reduced only in animals with CHF when compared with age-matched controls (BIO.RB). Total microsomal protein and p-nitrophenol glucuronidation were not affected by the disease process. We conclude that the reduction in cytochrome P-450 levels and N-demethylase activity in cardiomyopathic hamsters is not a consequence of CHF, but is one of the manifestations of the disease process.

Evidence for presence of a reduced form of digoxin-like immunoreactive factor (dihydro-DLIF) in mammalian tissues

1996 ◽  
Vol 42 (7) ◽  
pp. 1092-1099 ◽  
Author(s):  
H M Qazzaz ◽  
S A Jortani ◽  
J M Poole ◽  
R Valdes
Keyword(s):  
Lactone Ring ◽  
Fold Increase ◽  
Cross Reactivity ◽  
Reduced Form ◽  
Molar Ratio ◽  
Endogenous Ligand ◽  
Metabolic Route ◽  
Mammalian Tissues ◽  
Spectral Absorbance ◽  
Cytochrome P 450

Abstract Digoxin-like immunoreactive factor (DLIF) from adrenal glands is an endogenous ligand structurally related to the plant-derived cardiac glycoside digoxin. Cardiac glycosides regulate the activity of the sodium pump and thus play key roles in disease processes involving regulation of ion transport. We now report the discovery of an endogenous dihydro-DLIF analogous to dihydrodigoxin. We used HPLC, ultraviolet spectrophotometry, and cross-reactivity with two antibodies, one specific for digoxin and one for dihydrodigoxin, to support the hypothesis that dihydro-DLIF contains a chemically reduced lactone ring. The spectral absorbance maximum for dihydro-DLIF is at 196 nm, identical to dihydrodigoxin. DLIF and dihydro-DLIF are 975- and 2588-fold less immunoreactive than digoxin and dihydrodigoxin for their respective antibodies. The molar ratio of dihydro-DLIF to DLIF is approximately 5.3 in bovine adrenocortical tissue and approximately 0.38 in human serum. Dihydrodigoxin (reduced lactone ring) added to microsomes isolated from bovine adrenal cortex produced a 4.5-fold increase in digoxin-like immunoreactivity (oxidized lactone ring) after 3 h of incubation. The biotransformation is likely mediated by a cytochrome P-450 NADPH-dependent process. Our findings demonstrate the presence of a dihydro-DLIF in mammals and suggest a metabolic route for synthesis of endogenous DLIF in mammalian tissue.

scholarly journals Neurosteroid metabolism. 7α-Hydroxylation of dehydroepiandrosterone and pregnenolone by rat brain microsomes

1992 ◽  
Vol 288 (3) ◽  
pp. 959-964 ◽  
Author(s):  
Y Akwa ◽  
R F Morfin ◽  
P Robel ◽  
E E Baulieu
Keyword(s):  
Rat Brain ◽  
Microsomal Protein ◽  
Optimal Conditions ◽  
Hydroxylated Metabolites ◽  
Enzymic Reaction ◽  
Polar Metabolites ◽  
Brain Microsomes ◽  
Prepubertal Rats ◽  
Derivatives Of

Two ‘neurosteroids’, dehydroepiandrosterone (DHEA) and pregnenolone (PREG), are converted by rat brain microsomes into polar metabolites, identified as the respective 7 alpha-hydroxylated (7 alpha-OH) derivatives by the ‘twin ion’ technique of g.l.c.-m.s. with deuterated substrates. The enzymic reaction requires NADPH and is stimulated 2-4-fold by EDTA. Under optimal conditions (pH 7.4, 0.5 mM-NADPH, 1 mM-EDTA), the Km values for DHEA and PREG are 13.8 and 4.4 microM respectively, and the Vmax. values are 322 and 38.8 pmol/min per mg of microsomal protein respectively. Trace amounts of putative 7 beta-OH derivatives of DHEA and PREG are detected. Oestradiol, at a pharmacological concentration of 5 microM, inhibits DHEA and PREG 7 alpha-hydroxylation. Formation of 7 alpha-hydroxylated metabolites is low in prepubertal rats and increases 5-fold in adults. Derivatives of PREG and DHEA, such as PREG sulphate, DHEA sulphate, progesterone and 3 alpha-hydroxy-5 alpha-pregnan-20-one, are known to be neuroactive. Therefore the quantitatively important metabolism to 7 alpha-OH compounds may contribute to the control of neurosteroid activity in brain.

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