Excretion of various porphyrins and their corresponding porphyrinogens by rabbits after intravenous injection

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Abstract
In normal rabbits, intravenously admin-istered uroporphyrin III and uroporphyrinogen III were both excreted exclusively in the urine. Injected coproporphyrinogen III was excreted in part in the urine, the addition or reducing agents or prior saturation of the animal with ascorbic acid increasing the proportion so excreted. The dicarboxylic porphyrins and porphyrinogens were not excreted in the urine in more than traces after injection. There was a significant urinary excretion of injected coproporphyrin III after carbon tetra-choloride poisoning but not after Pb poisoning. Injection of coproporphyrin III into the rabbit with a ligated common bile duct was followed by excretion of coproporphyrin HI in the urine. The concentration rose during the first 4 hours after which it remained at a high level. Between 50 and 67% of the dose was so excreted before death. There was coincident bilirubinuria and hematuria. Determination of blood porphyrin or porphyrinogen concentrations after injection of coproporphyrin III or coproporphyrinogen HI into normal rabbits and rabbits with surgical ligature of the common bile duct showed that there is an avid uptake of these materials, presumably by the liver, resulting in rapidly falling blood concentrations. When biliary excretion was prevented, however, pigment returned to the blood stream where its concentration remained elevated for a considerable time. The metabolic conversion in vivo of coproporphyrinogen HI into protoporphyrin was demonstrated. There was no detectable conversion of uroporphyrinogen HI into coproporphyrinogen III.
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