Cytochrome P-450-dependent 6 beta-hydroxylation of bile acids in rat liver contributes to the synthesis of the quantitatively important pool of 6-hydroxylated bile acids, as well as to the detoxification of hydrophobic bile acids. The lithocholic acid 6 beta-hydroxylation reaction was investigated and compared with androstenedione 6 beta-hydroxylation. Differential responses of these two activi...

Inhibition of protein synthesis superinduces transcription of the cytochrome P1-450 gene in Hepa 1c1c7 mouse hepatoma cells. The superinduced transcription rate is 10-15-fold higher than the maximal rate of transcription induced by the known inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alone. Superinduction is maximal within 30-40 min and remains maximal for at least 90 min. Cytochrome P1...

The oxidation of ethanol by a reconstituted system containing NADPH-cytochrome P-450 reductase and cytochrome P-450 from phenobarbital-treated rats was characterized especially with regard to the role of oxygen radicals in the mechanism of ethanol oxidation. Results described in the preceding manuscript demonstrated that a strong oxidizing species with properties similar to that of the hydroxyl...

Some quinolone antibiotics cause increases in levels of theophylline in plasma that lead to serious adverse effects. We investigated the mechanism of this interaction by developing an in vitro system of human liver microsomes. Theophylline (1,3-dimethylxanthine) was incubated with human liver microsomes in the presence of enoxacin, ciprofloxacin, norfloxacin, or ofloxacin. Theophylline, its dem...

By using 3-amino-1,2,4-triazole, an inhibitor of haem synthesis, and 2-allyl-2-isopropylacetamide, a drug that degrades the haem moiety of cytochrome P-450, the involvement of haem in cytochrome P-450 synthesis and assembly was investigated. Phenobarbital was used to stimulate apo-(cytochrome P-450) synthesis. Degradation of preformed cytochrome P-450 haem does not result in a concomitant relea...

PURPOSE To study the toxicity and pharmacokinetic-pharmacodynamic profile of 17-allylamino, 17- demethoxygeldanamycin (17-AAG) and to recommend a dose for phase II trials. PATIENTS AND METHODS This was a phase I study examining a once-weekly dosing schedule of 17-AAG. Thirty patients with advanced malignancies were treated. RESULTS The highest dose level reached was 450 mg/m(2)/week. The do...

Effects of Lead on the Induction of Hepatic Microsomal Enzymes by Phenobarbital and 3,4Benzpyrene. CHOW, C. P. AND CORNISH, H. H. (1978). Toxicol. Appl. Pharmacol. 43,219-228. A single ip injection of lead acetate (65 mg/kg) prolonged the duration of zoxazolamine paralysis in Sprague-Dawley rats and prevented the stimulation of zoxazolamine metabolism normally induced by phenobarbital. Lead als...

Goat antibody IgG produced against bovine corpus luteum mitochondrial cytochrome P-450 (P-450scc) associated with cholesterol side chain cleavage (CSCC) was used to compare immunological characteristics of mitochondrial cytochrome P-450s from the bovine adrenal cortex (BAM), bovine corpus luteum (BCLM), and human placenta (HPM). In Ouchterlony double diffusion, anti-P450scc produced a single ba...

NADPH-cytochrome P-450 oxidoreductase (CPR) is essential for the catalytic activity of cytochrome P-450 (P-450). On a molar basis, the amount of P-450 exceeds that of CPR in human liver. In this study, we investigated whether drug-drug interactions can occur as a result of competition between P-450 isozymes for this ancillary protein. For this purpose, combinations of P-450 isozymes were coexpr...

In erythropoietic protoporphyria, accumulation of protoporphyrin has been found in various tissues and liver cirrhosis occurs frequently in this disease, probably due to toxic dark effects of protoporphyrin. We have studied the effect of porphyrins on various enzymic functions in rat liver microsomes. Incubation of microsomes with protoporphyrin resulted in a concentration-dependent inhibition ...