Studies of Coproporphyrin. I. the per Diem Excretion and Isomer Distribution of Coproporphyrin in Normal Human Urine.

A recent review (1) has dealt with previous studies of the urinary coproporphyrins, both as carried out in this laboratory and elsewhere. The purpose of the present series of communications is to provide newer data relating to various aspects of the coproporphyrin problem. It is well known that two of the four coproporphyrin isomers occur in human urine (1).. These naturally occurring isomers are types I and III according to H. Fischer's classification, as based upon the configuration of the four artificial aetioporphyrins (2). Apart from the difference displayed by the two isomers in ester melting point and crystal habitus, a differing physical behavior has been described Us manifested in their pH fluorescence curves. This difference was first noted by Hoerburger and Fink (3-5) who attempted to apply it to the coproporphyrin of normal urine. The crystal habitus and pH fluorescence curve of the few crystals which they obtained indicated the presence of coproporphyrin I (5). A later study by Watson (6) was likewise somewhat indecisive in that the melting point of the crystalline ester was 2280 C, that of pure coproporphyrin I methyl ester being 2520 C (corrected), as contrasted with the varying or dimorphic melting point of the esters of coproporphyrin III: 1340, 1420, 1680 (2). The crystal habitus in this study also, was that of the type I isomer, and it was therefore concluded that in the urine employed, which was from one normal individual, the preponderant coproporphyrin was type I. At the same time it was believed that a small amount of the type III isomer was present, since a few rosettes of prisms having the type III habitus were obtained from the mother liquor. The weighed yield of crystals in