Photosensitive or Congenital Porphyria with Hemolytic Anemia : II. Isotopic Studies of Porphyrin and Hemoglobin Metabolism

1. Porphyrin and hemoglobin metabolism have been studied in a case of photosensitive or congenital porphyria with the aid of glycine containing N¹⁵. The case was that of a 4 year old girl who also exhibited splenomegaly and hemolytic anemia. The reticulocytes and fecal urobilinogen were markedly increased and the bone marrow was hyperplastic-normoblastic. The urine contained large amounts of uroporphyrin I and lesser amounts of coproporphyrin I, while the reverse was true in the feces. Splenectomy resulted in disappearance of anemia, together with marked reduction of porphyrin excretion.

2. In two separate periods of study a rapid incorporation of glycine N¹⁵ was observed in the hemoglobin protoporphyrin, in both coproporphyrin isomers of the urine and in the type I isomer in the feces; also in the uroporphyrin I of the urine, and in the protoporphyrin and stercobilin of the feces.

3. The N¹⁵ data obtained for the urinary and fecal coproporphyrin and the urinary uroporphyrin, clearly reveal a synthesis similar in character to that of the hemoglobin protoporphyrin. The striking decline in formation of copro- and uroporphyrin after splenectomy is believed to be correlated directly with the reduced erythropoiesis incident to removal of the excessive hemolysis.

4. In both experiments the peak concentration of N¹⁵ was earlier and greater in the copro- than in the uroporphyrin. This, together with the closely similar slopes of decrease of the N¹⁵ curves for the two substances, does not appear to support a transition of uro- to coproporphyrin in the present case. The data are more consistent with the view that coproporphyrin I is a precursor of uroporphyrin I, or that both porphyrins are synthesized independently from common precursors.

5. The amount of coproporphyrin III in the excreta was too small to permit N¹⁵ analysis except in one period early in the first experiment; here the value was approximately the same as that of the copro- I for the same period, indicating a closely related synthesis.