抄録
Dicarboxylic porphyrins, such as proto, meso, deutero, etc. are not excreted into urine but into bile4), however small amounts of protoporphyrin are often determined at the determination of urinary coproporphyrin1). Chiba2) reported urinary protoporphyrin in rabbits suffering from tin poisoning. Small amounts of tricarboxylic porphyrin have been found in the urine of animals with lead poisoning3). Since proto and tricarboxylic porphyrin have a simillar acid solubility, there is a possibility of confuse between these two porphyrins.
In order to determine free porphyrin and the metylester of the porphyrins, paper chromatography using a lutidine-water system and thin layer chromatography using a benzene-ethylacetate system were respectively employed. The metylester gave a pattern typical of etio-type porphyrins with a Soret maximum of 404nm in a CHCl3 solution. Although tricarboxylic porphyrin in urine was eatimated to be at a level of only 3% of that of coproporphyrin in both normal and lead-poisoned rabbits, there was a heigh correlation (r=0.932, n=49) between the amounts both in urine.
The results suggest that urinary tricarboxylic porphyrin is an intermediate substance deriving during the process of oxidative decarboxylation from coproporphyrinogen to protoporphyrinogen and, that excretion of the pigment may be increased by lead, because lead disturbs certain stages of porphyrin biosynthesis. Intermediates in the pathway may, therfore, accumulate in vivo. The amount of urinary tricarboxylic porphyrin is thought to be of little value as an indicator of lead poisoning because of the complicated required to assertain it. Coproporphyrin, on the other hand, does not present such technical difficulties.
