Clinical Chemistry, Vol 6, 71-97, Copyright © 1960 by the American Association for Clinical Chemistry

Studies of the Uroporphyrins

VI. Isomer composition of the "Waldenströmporphyrins;" effect of heat and the significance of porphyrinogen

¹ Department of Medicine, University of Minnesota Hospitals, Minneapolis, Minn.

1. Seventeen cases of hepatic porphyria have been studied with respect to variations in isomer composition of the urinary Waldenström uroporphyrin complex.

2. Comparison was made of the effect of various isolation procedures on the isomer composition of the uroporphyrin complex, with special reference to the effect of preliminary heating of the urine.

3. Methods not employing heat, including the ethyl acetate extraction procedure of Waldenström, the talc adsorption of Grinstein et al., and a number of modifications, usually yielded relatively small amounts of a uroporphyrin complex, preponderantly Type I isomer. In two instances, however, the complex contained 60-70 per cent Type III. When separable on calcium carbonate, the Type III component was again shown to consist in the main of a 7-COOH porphyrin. Preheating of the urine regularly produced much larger amounts of a Waldenström type porphyrin, and larger proportions of Type III isomer in the complex.

4. The Waldenström porphyrin isolated following conversion of naturally occurring porphyrinogen, by irradiation with ultraviolet light, usually contained a marked preponderance of uroporphyrin I. In certain instances, however, the porphyrinogen was entirely that of the "208" Type III porphyrin.

5. While the large amount of Type III porphyrin found after heating the urine undoubtedly represents nonenzymatic conversion of porphobilinogen, the smaller amount of Type I isomer usually present in major proportion in the preformed uroporphyrin complex or its porphyrinogen may have intrinsic metabolic significance. In exceptional cases of acute porphyria, the uroporphyrin of the unheated urine is preponderantly the Type III isomer.