title: Mechanisms of diethyldithiocarbamate-induced loss of cytochrome P-450 from rat liver.
abstract: A single, intraperitoneal injection of diethyldithiocarbamate (DDTC) to adult, male Sprague-Dawley rats decreased hepatic cytochrome P-450 (P-450) concentrations. This effect was dose-dependent over a range of 250 to 750 mg/kg and most prominent 24-36 hr after dosing. Depletion of hepatic glutathione (GSH) by diethylmaleate (DEM) administration significantly decreased P-450 8 hr after concurrent treatment with DDTC at a dose which given alone had little effect on P-450 concentrations. When hepatic microsomes were incubated with DDTC in the presence of NADPH, P-450 was converted to cytochrome P-420 (P-420). Similar incubations employing [35S]DDTC demonstrated strict NADPH-dependent binding of labeled sulfur to microsomal membranes, suggesting that diminished P-450 concentrations are related to the metabolic activation of DDTC. Addition of reduced GSH to incubation mixtures blocked the binding of 35S to microsomal membranes, as well as conversion of P-450 to P-420. DDTC inhibited NADPH-ADP3+ mediated peroxidation of microsomal lipids in vitro, suggesting that the effect of DDTC on P-450 does not result from stimulation of lipid peroxidation, but may be influenced by the levels of hepatic GSH. DDTC treatment 1 hr after P-450 was pulse labeled by an intravenous injection of [3H]delta-aminolevulinic acid resulted in a 2-fold increase in the rate of loss of radioactivity associated with membrane-bound P-450 heme during the next 20 hr. Within this time interval, hepatic heme oxygenase (HO) activity increased and at 8 hr after dosing was 7-fold greater than control values in the livers, but was unchanged in the kidneys and spleens of DDTC-treated animals. An elevation of hepatic delta-aminolevulinic acid synthetase (delta-ALAS) activity occurred at 8 and 24 hr after DDTC treatment. Since this enzyme is rate limiting in the biosynthesis of heme, its increased activity may represent a compensatory response to offset the DDTC-mediated loss of P-450 heme.
mesh_terms: D000624:5-Aminolevulinate Synthetase / Q000032:analysis; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis*; D004050:Ditiocarb / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000494:pharmacology; D006418:Heme / Q000032:analysis; D006420:Hemeproteins / Q000032:analysis; D066298:In Vitro Techniques; D008054:Lipid Peroxides / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013859:Thiocarbamates / Q000494:pharmacology*
chemical_list: D006420:Hemeproteins; D008054:Lipid Peroxides; D013859:Thiocarbamates; D006418:Heme; D003577:Cytochrome P-450 Enzyme System; D004050:Ditiocarb; D000624:5-Aminolevulinate Synthetase; D005978:Glutathione