Degradation of heme IX in rats pretreated with cobaltous chloride. A study in isolated perfused liver

The effect of the administration of cobaltous chloride on the degradation of heme IX was investigated using perfusions of isolated rat livers. The presence of biliverdin IX beta (2%) in the bile fluid of cobaltous chloride treated rats support the hypothesis of the presence of a chemical oxidation of heme IX induced by the cobalt salt. In control rats the absence of biliverdin IX beta in the bile fluid was observed. When biliverdin IX beta was added to the perfusate it was excreted in the bile fluid as bilirubin IX beta without conjugation. An increase from approximately twofold to three-fold of the total bilirubins in the bile fluids of cobaltous chloride pretreated rats in relation with control rats was observed due to heme oxygenase enhanced activity. Bilirubin IX alpha diconjugates increased ca. 15% in the bile fluids of cobaltous chloride pretreated rats, after the addition of hemin IX. The increase could reflect the presence of a new molecular form of UDP-glucuronosyltransferase, which favours the formation of bilirubin IX alpha diglucuronide and therefore its preferential excretion into the bile. In the bile fluid of the rats pretreated with cobaltous chloride, other diconjugates of bilirubin IX alpha were also detected 120 min after the addition of hemin IX to the perfusate, consisting of glucose and glucuronate (5%) and xylose and glucuronate (5%).