title: The cytochrome P-450-depleted animal: an experimental model for in vivo studies in chemical biology.
abstract: An experimental method is described to deplete markedly in vivo the cytochrome P-450 content of liver for prolonged periods of time. The method uses the synthetic metalloporphyrin cobalt-heme (cobalt protoporphyrin IX), which possesses the dual biological properties of repressing delta-aminolevulinate synthase, the rate-limiting enzyme of heme biosynthesis, and of potently inducing microsomal heme oxygenase, the rate-limiting enzyme of heme catabolism. A single dose of cobalt-heme (125 mumol/kg of body weight) decreased within 48 hr hepatic cytochrome P-450 to approximately 20% of normal, at which level it remained for 10 days; normal levels were not achieved by 36 days. Periodic administration (total, six injections) of a smaller dose of cobalt-heme (50 mumol/kg of body weight) maintained the cytochrome P-450 content at levels approximately 15% of normal for greater than 90 days with concurrent profound impairment of mono-oxygenase reactions catalyzed by this heme protein. The ability of cobalt-heme to produce profound and prolonged depletion of cytochrome P-450 in vivo provides a valuable model for examining the role of cytochrome P-450-dependent metabolism in the biology of endogenous and exogenous chemicals.
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000172:deficiency*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D008099:Liver / Q000378:metabolism; D008297:Male; D011166:Porphyrins / Q000009:adverse effects*; D011524:Protoporphyrins / Q000009:adverse effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D011166:Porphyrins; D011524:Protoporphyrins; C007095:cobaltiprotoporphyrin; D003577:Cytochrome P-450 Enzyme System