Hexachlorobenzene porphyria in the rat provides a suitable experimental model of the stages of development of human chronic hepatic porphyria. Just as in chronic hepatic porphyria in man, the development of experimental HCB porphyria in the rat can be divided into several stages. 2. The findings in this study indicate that porphyrins increase in the urine, liver, kidney, and spleen, and to a lesser degree in the serum, with uroporphyrin and heptacarboxylic porphyrin predominating. 3. In contrast to the distribution of porphyrin accumulation in the various organs, clear evidence of a uroporphyrinogen decarboxylase defect was found only in the liver. Formation of uroporphyrin and heptacarboxylic porphyrin by homogenized HCB kidney tissue did not deviate significantly from that by control kidney. The defect could not be unequivocally evaluated in the spleen because the spleen, like the red cells, normally forms considerable amounts of uroporphyrin from porphobilinogen, which were increased only a few times over in synthesis by the HCB spleen. 4. Isomer studies provide no evidence for an additional uroporphyrinogen cosynthase defect.
