title: Tissue distribution and disposition of tin-protoporphyrin, a potent competitive inhibitor of heme oxygenase.
abstract: Tin(Sn)-protoporphyrin is a potent competitive inhibitor of heme oxygenase and can also suppress naturally occurring or experimentally induced hyperbilirubinemia in animals. In this study we examined the plasma clearance of Sn-protoporphyrin, its persistence in tissues and the time course of heme oxygenase inhibition up to 7 days after administration of doses up to 50 mumol/kg b.w. to adult male rats. After s.c. doses the metalloporphyrin was rapidly and almost completely absorbed. Initial plasma clearance was log-linear with a T 1/2 of approximately 3 h after either i.v. or s.c. administration. Levels of Sn-protoporphyrin in most tissues rose during the first 2 h and persisted for up to 7 days. Concentrations were highest in kidney and liver, were considerably lower in spleen, lung, intestine, adrenal and testes, and as Sn-protoporphyrin concentrations in plasma declined, concentrations in these tissues eventually exceeded simultaneous plasma concentrations. This suggests a varying degree of uptake and binding of the metalloporphyrin in these tissues. There was little or no uptake of Sn-protoporphyrin in heart, brain and red cells. Markedly decreased heme oxygenase activity in liver, kidney and spleen persisted as did Sn-protoporphyrin up to 7 days. The total amount of Sn-protoporphyrin present in tissues and excreta was a fairly constant fraction of the dose (approximately 50%) at time intervals up to 7 days after injection. These results indicate that single doses of Sn-protoporphyrin are rapidly cleared from plasma and persist in tissues and potently inhibit heme oxygenase activity for prolonged periods.
mesh_terms: D000818:Animals; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors*; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D008665:Metalloporphyrins; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors*; D011166:Porphyrins / Q000378:metabolism*; D011524:Protoporphyrins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013050:Spectrometry, Fluorescence; D013154:Spleen / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D008665:Metalloporphyrins; D011166:Porphyrins; D011524:Protoporphyrins; C032628:tin protoporphyrin IX; D006899:Mixed Function Oxygenases; D006419:Heme Oxygenase (Decyclizing)