Metabolism reduction

Spin probes are quite readily metabolized reductively by cells and have been utilized to monitor metabolic activity (lannore etal., 1990) The line widths of the e.s.r. signals are also sensitive to the presence of O2 in both intracellular and extracellular environments and hence O2 concentrations may be determined with TBN or alternative spin probes (Glockner and Swartz, 1991). 

The In vitro metabolic reduction of nitro PAHs was first reported in 1967 (124). Since then a number of similar investigations have been conducted however, most of these studies have been performed under only anaerobic conditions. The oxidative metabolism of nitro PAHs has been examined only recently, but as considered in the following sections, both reductive and oxidative metabolic pathways may be important in the metabolic activation of nitro PAHs. 

Minoshima, S., Giordani, B., Berent, S. et al. Metabolic reduction in the posterior cingulate cortex in very early Alzheimer s disease. Ann. Neurol. 42 85-94,1997. 

Rinde E, Troll W. 1975. Metabolic reduction of benzidine azo dyes to benzidine in rhesus monkey. JNatl Cancer Inst 55(1) 181-182. 

In addition, another organosulfur compound, S-allyl-mercaptocysteine (Fig. 2) has been shown to affect histone acetylation levels. This again is probably due to its ability to form allyl mercaptan upon metabolic reduction of its disulfide bond. ... 

Mendeleyev J, Kirsten E, Hakam A et al (1995) Potential chemotherapeutic activity of 4-iodo-3-nitrobenzamide metabolic reduction to the 3-nitroso derivative and induction of cell death in tumor cells in culture. Biochem Pharmacol 50 705-714... 

Curcumin (diferuloylmethane) has very low oral bioavailability, but is rapidly absorbed and low nanomolar levels of the parent compound and its glucuronide and sulfate conjugates can be detected in human plasma and portal circulation after very high (nondietary) intakes (3.6g/day for 1 week). Metabolic reduction occurs in the liver, and glutathione adducts have been observed in vitro ... 

Substitute treatments are based on research that has found a metabolic reduction of several neurotransmitters in the brain. 

Challenger mechanism Also called the Challenger scheme, which was proposed by Frederick Challenger. The mechanism is a series of metabolic reduction and oxidative methylation reactions that begin with the reduction of inorganic arsenate to inorganic arsenite and ultimately ends with the formation of trimethy-larsine. See Chapters 2 and 4 for details. 

Table 7.1 Functional Groups That Undergo Metabolic Reduction... 

The mechanism in hepatic cellular metabolism involves an electron transport system that functions for many drugs and chemical substances. These reactions include O-demethylation, N-demethyla-tion, hydroxylation, nitro reduction and other classical biotransformations. The electron transport system contains the heme protein, cytochrome P-450 that is reduced by NADPH via a flavoprotein, cytochrome P-450 reductase. For oxidative metabolic reactions, cytochrome P-450, in its reduced state (Fe 2), incorporates one atom of oxygen into the drug substrate and another into water. Many metabolic reductive reactions also utilize this system. In addition, there is a lipid component, phosphatidylcholine, which is associated with the electron transport and is an obligatory requirement for... 

Thus the metabolic reduction of chromium(VI) may represent bioactivation and/or detoxification. If a bioactivation process, intracellular reduction of chromium(VI) would lead to the ultimate toxic species. Conversely, if chromium(VI) is the toxic agent, effects would be elicited only if the amount of chromium(VI) entering target cells saturates the reducing mechanisms. 

Petrilli FL, Camoirano A, Bennicelli C, et al. 1985. Specificity and inducibility of the metabolic reduction of chromium(VI) mutagenicity by subcellular fractions of rat tissues. Cancer Res 45 3179-3187. 

Petrilli FL, Romano M, Bennicelli C, et al. 1986a. Metabolic reduction and detoxification of hexavalent chromium. In Serrone DM, ed. Chromium symposium 1986 An update. Pittsburgh, PA Industrial Health Foundation Inc., 112-130. 

Petrilli FL, Rossi GA, Camoirano A, et al. 1986b. Metabolic reduction of chromium by alveolar macrophages and its relationships to cigarette smoke. J Clin Invest 77 1917-1924. 

Low Excreted mainly as metabolites Excreted as metabolites in faeces Eirst-pass metabolism Reduction then conjugated with glucuronide or sulfate Norethisterone 5a-dihydronorethisterone Tetrahydronorethisterone... 

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