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In vivo and in vitro biotransformation of theobromine by phenobarbital- and 3-methylcholanthrene-inducible cytochrome P-450 monooxygenases in rat liver. Role of thiol compounds.
Drug Metab Dispos. 1987 Mar-Apr; 15(2):217-24.DM

Abstract

A new in vitro method was developed and applied to establish the role of the hepatic cytochrome P-450 monooxygenases in theobromine biotransformation by control and phenobarbital (PB)- and 3-methylcholanthrene (3MC)-induced Sprague-Dawley rats. In vivo theobromine metabolite formation and pharmacokinetic parameters were also determined to serve as a comparison for in vitro studies. In vivo, the major urinary metabolite was 6-amino-5-[N-methylformylamino]-1-methyluracil (3,7DAU) with lesser amounts of 3,7-dimethyluric acid (3,7DMU), 3-methylxanthine, 7-methylxanthine, 7-methyluric acid, and traces of dimethylallantoin (DMA). Following induction with 3MC, but not PB, selective increases occurred in the urinary excretion of 3,7DAU, indicating that a 3MC-inducible cytochrome P-450 isozyme plays a significant role in this metabolic pathway. Both PB and 3MC induction increased slightly urinary elimination of DMA, a minor metabolite. Pharmacokinetic studies after a single oral dose of 5 mg/kg theobromine revealed a marked effect of 3MC treatment on theobromine elimination, as evidenced by a 59% decrease in theobromine t1/2, a 75% decrease in AUC, and a 284% increase in clearance. By contrast, PB had no effect. Fecal 14C elimination accounted for approximately 5% of the administered theobromine dose, and biliary excretion studies revealed the presence of 3,7DMU, DMA, 3,7DAU, and unchanged theobromine. Studies in vitro indicated that 3,7DMU was the major theobromine metabolite produced by liver microsomes. Conversion rates in PB- and 3MC-induced rats were 2- and 11-fold higher, respectively, than in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Authors

No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

2882982

Citation

Shively, C A., and E S. Vesell. "In Vivo and in Vitro Biotransformation of Theobromine By Phenobarbital- and 3-methylcholanthrene-inducible Cytochrome P-450 Monooxygenases in Rat Liver. Role of Thiol Compounds." Drug Metabolism and Disposition: the Biological Fate of Chemicals, vol. 15, no. 2, 1987, pp. 217-24.
Shively CA, Vesell ES. In vivo and in vitro biotransformation of theobromine by phenobarbital- and 3-methylcholanthrene-inducible cytochrome P-450 monooxygenases in rat liver. Role of thiol compounds. Drug Metab Dispos. 1987;15(2):217-24.
Shively, C. A., & Vesell, E. S. (1987). In vivo and in vitro biotransformation of theobromine by phenobarbital- and 3-methylcholanthrene-inducible cytochrome P-450 monooxygenases in rat liver. Role of thiol compounds. Drug Metabolism and Disposition: the Biological Fate of Chemicals, 15(2), 217-24.
Shively CA, Vesell ES. In Vivo and in Vitro Biotransformation of Theobromine By Phenobarbital- and 3-methylcholanthrene-inducible Cytochrome P-450 Monooxygenases in Rat Liver. Role of Thiol Compounds. Drug Metab Dispos. 1987 Mar-Apr;15(2):217-24. PubMed PMID: 2882982.
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TY - JOUR T1 - In vivo and in vitro biotransformation of theobromine by phenobarbital- and 3-methylcholanthrene-inducible cytochrome P-450 monooxygenases in rat liver. Role of thiol compounds. AU - Shively,C A, AU - Vesell,E S, PY - 1987/3/1/pubmed PY - 1987/3/1/medline PY - 1987/3/1/entrez SP - 217 EP - 24 JF - Drug metabolism and disposition: the biological fate of chemicals JO - Drug Metab Dispos VL - 15 IS - 2 N2 - A new in vitro method was developed and applied to establish the role of the hepatic cytochrome P-450 monooxygenases in theobromine biotransformation by control and phenobarbital (PB)- and 3-methylcholanthrene (3MC)-induced Sprague-Dawley rats. In vivo theobromine metabolite formation and pharmacokinetic parameters were also determined to serve as a comparison for in vitro studies. In vivo, the major urinary metabolite was 6-amino-5-[N-methylformylamino]-1-methyluracil (3,7DAU) with lesser amounts of 3,7-dimethyluric acid (3,7DMU), 3-methylxanthine, 7-methylxanthine, 7-methyluric acid, and traces of dimethylallantoin (DMA). Following induction with 3MC, but not PB, selective increases occurred in the urinary excretion of 3,7DAU, indicating that a 3MC-inducible cytochrome P-450 isozyme plays a significant role in this metabolic pathway. Both PB and 3MC induction increased slightly urinary elimination of DMA, a minor metabolite. Pharmacokinetic studies after a single oral dose of 5 mg/kg theobromine revealed a marked effect of 3MC treatment on theobromine elimination, as evidenced by a 59% decrease in theobromine t1/2, a 75% decrease in AUC, and a 284% increase in clearance. By contrast, PB had no effect. Fecal 14C elimination accounted for approximately 5% of the administered theobromine dose, and biliary excretion studies revealed the presence of 3,7DMU, DMA, 3,7DAU, and unchanged theobromine. Studies in vitro indicated that 3,7DMU was the major theobromine metabolite produced by liver microsomes. Conversion rates in PB- and 3MC-induced rats were 2- and 11-fold higher, respectively, than in controls.(ABSTRACT TRUNCATED AT 250 WORDS) SN - 0090-9556 UR - https://www.unboundmedicine.com/medline/citation/2882982/In_vivo_and_in_vitro_biotransformation_of_theobromine_by_phenobarbital__and_3_methylcholanthrene_inducible_cytochrome_P_450_monooxygenases_in_rat_liver__Role_of_thiol_compounds_ DB - PRIME DP - Unbound Medicine ER -