Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The chlorinated dibenzo-p-dioxins and dibenzofurans are formed as trace contaminants during the synthesis of a number of commercially important chemicals. The prototype compound of this group, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is one of the most potent low molecular weight toxins and teratogens known, and its inadvertent dispersion in the environment has caused concern about the potential hazard to human health. In studying the biochemical effects of TCDD, it was found to be extraordinarily potent as an inducer of two hepatic enzymes: 1) delta-aminolevulinic acid synthetase, the initial and rate-limiting enzyme in heme synthesis, and 2) aryl hydrocarbon hydroxylase, a cytochrome P-450-mediated microsomal monooxygenase. Among a series of halogenated dibenzo-p-dioxins there is an excellent correlation between their toxic potency and their potency as inducers of these two enzymes. The administration of polycyclic aromatic hydrocarbons (e.g., 3-methylcholanthrene (MC)) to certain inbred strains of mice induces aryl hydrocarbon hydroxylase, while other inbred strains fail to respond; and the trait of aryl hydrocarbon responsiveness is inherited as an autosomal dominant. TCDD, about 30,000 times as potent as MC, induces all strains whether responsive or nonresponsive to MC; however, the responsive strains are more sensitive (ED 50 approximately 1 X 10(-9) mole/kg) to TCDD than are the nonresponsive strains (ED50 larger than or equal to 1 X 10(-8) mole/kg). The results suggest that the mutation in the nonresponsive strains results in a ligand binding site (an induction receptor) that has a diminished affinity for MC and TCDD. The correlation among the halogenated dibenzo-p-dioxins, between their potency as toxins and their potency as inducers of aryl hydrocarbon hydroxylase, is discussed in relationship to various proposed mechanisms of toxicity.
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PMID:2,3,7,8-Tetrachlorodibenzo-p-dioxin: environmental contaminant and molecular probe. 13 10

A comparative study of the ability of phenobarbital, testosterone and their combination to induce the liver microsomal monooxygenase system after 9-day administration of these compounds to intact male and female rats was carried out. It was shown that administration of testosterone does not increase the level of cytochromes P450 and b5 in the livers of male and female rats. However, after a combined administration of the two compounds testosterone significantly enhances the inducing effects of phenobarbital (i. e. superinduction) in female rats; no such effect was observed in the livers of male rats. The rates of oxidation of hexobarbital, ethylmorphine and testosterone by liver microsomes are also increased after a combined administration of the two inducers. However, the additive effects of the two substances on substrate oxidation are observed when the latter was calculated per mole of cytochrome P450. An administration of testosterone to male rats does not result in an increase of the rate of hexobarbital and testosterone oxidation by isolated liver microsomes.
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PMID:[Induction of the microsomal monooxygenase system of rat liver by combined administration of testosterone and phenobarbital]. 50 68