Biomaterial Database

Lack of relationship between debrisoquine 4-hydroxylation and other cytochrome P-450 dependent reactions in rat and human liver. 1985

T Wolff, and M Strecker

The effect of various inhibitors and inducers of cytochrome P-450 on the activity of microsomal debrisoquine 4-hydroxylation (DQH) was investigated in rat liver. DQH was strongly inhibited by SKF 525-A, 7,8-benzoflavone, and metyrapone. Pretreatment of animals with common inducers, such as phenobarbital, 3-methylcholanthrene, the commercial PCB mixture, Clophen A-50, dexamethasone and pregenenolone-16 alpha-carbonitrile did not lead to induction of DQH, while most reference reactions, i.e. aldrin epoxidation, ethylmorphine demethylation, and benzo(a)-pyrene hydroxylation were induced under these conditions. DQH likewise was not induced by pretreatment of animals with the enzyme substrate DQ. The relationship between DQH and other cytochrome P-450 functions was also studied in untreated animals. Both genders of Wistar rats exhibited similar rates of DQH, but different activities of the reference reactions. DQH activity in Wistar females however, was 10 times higher than in females of the DA-strain, whereas the reference activities were similar in both strains. The studies were also extended to human liver. DQH activity in homogenates of various biopsy samples was neither correlated to the activity of aldrin epoxidation nor to AHH activity. The results indicate that DQH in the rat and in man reflects the activity of a cytochrome P-450 species not related to various other known cytochrome P-450 functions.

UI	MeSH Term	Description	Entries
D007546	Isoquinolines	A group of compounds with the heterocyclic ring structure of benzo(c)pyridine. The ring structure is characteristic of the group of opium alkaloids such as papaverine. (From Stedman, 25th ed)
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008297	Male		Males
D008862	Microsomes, Liver	Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough.	Liver Microsomes,Liver Microsome,Microsome, Liver
D010634	Phenobarbital	A barbituric acid derivative that acts as a nonselective central nervous system depressant. It potentiates GAMMA-AMINOBUTYRIC ACID action on GABA-A RECEPTORS, and modulates chloride currents through receptor channels. It also inhibits glutamate induced depolarizations.	Phenemal,Phenobarbitone,Phenylbarbital,Gardenal,Hysteps,Luminal,Phenobarbital Sodium,Phenobarbital, Monosodium Salt,Phenylethylbarbituric Acid,Acid, Phenylethylbarbituric,Monosodium Salt Phenobarbital,Sodium, Phenobarbital
D011335	Proadifen	An inhibitor of drug metabolism and CYTOCHROME P-450 ENZYME SYSTEM activity.	Propyladiphenin,Diethylaminoethyldiphenylpropyl Acetate,Proadifen Hydrochloride,SK&F-525-A,SK-525A,SKF-525-A,SKF-525A,Acetate, Diethylaminoethyldiphenylpropyl,Hydrochloride, Proadifen,SK 525A,SK&F 525 A,SK&F525A,SK525A,SKF 525 A,SKF525A
D011919	Rats, Inbred Strains	Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding.	August Rats,Inbred Rat Strains,Inbred Strain of Rat,Inbred Strain of Rats,Inbred Strains of Rats,Rat, Inbred Strain,August Rat,Inbred Rat Strain,Inbred Strain Rat,Inbred Strain Rats,Inbred Strains Rat,Inbred Strains Rats,Rat Inbred Strain,Rat Inbred Strains,Rat Strain, Inbred,Rat Strains, Inbred,Rat, August,Rat, Inbred Strains,Rats Inbred Strain,Rats Inbred Strains,Rats, August,Rats, Inbred Strain,Strain Rat, Inbred,Strain Rats, Inbred,Strain, Inbred Rat,Strains, Inbred Rat
D003577	Cytochrome P-450 Enzyme System	A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism.	Cytochrome P-450,Cytochrome P-450 Enzyme,Cytochrome P-450-Dependent Monooxygenase,P-450 Enzyme,P450 Enzyme,CYP450 Family,CYP450 Superfamily,Cytochrome P-450 Enzymes,Cytochrome P-450 Families,Cytochrome P-450 Monooxygenase,Cytochrome P-450 Oxygenase,Cytochrome P-450 Superfamily,Cytochrome P450,Cytochrome P450 Superfamily,Cytochrome p450 Families,P-450 Enzymes,P450 Enzymes,Cytochrome P 450,Cytochrome P 450 Dependent Monooxygenase,Cytochrome P 450 Enzyme,Cytochrome P 450 Enzyme System,Cytochrome P 450 Enzymes,Cytochrome P 450 Families,Cytochrome P 450 Monooxygenase,Cytochrome P 450 Oxygenase,Cytochrome P 450 Superfamily,Enzyme, Cytochrome P-450,Enzyme, P-450,Enzyme, P450,Enzymes, Cytochrome P-450,Enzymes, P-450,Enzymes, P450,Monooxygenase, Cytochrome P-450,Monooxygenase, Cytochrome P-450-Dependent,P 450 Enzyme,P 450 Enzymes,P-450 Enzyme, Cytochrome,P-450 Enzymes, Cytochrome,Superfamily, CYP450,Superfamily, Cytochrome P-450,Superfamily, Cytochrome P450
D003647	Debrisoquin	An adrenergic neuron-blocking drug similar in effects to GUANETHIDINE. It is also noteworthy in being a substrate for a polymorphic cytochrome P-450 enzyme. Persons with certain isoforms of this enzyme are unable to properly metabolize this and many other clinically important drugs. They are commonly referred to as having a debrisoquin 4-hydroxylase polymorphism.	Debrisoquine,Tendor
D004790	Enzyme Induction	An increase in the rate of synthesis of an enzyme due to the presence of an inducer which acts to derepress the gene responsible for enzyme synthesis.	Induction, Enzyme