PORPHYRINS 



284 



PORPHYRINS 



but could be recognized by their fluores- 

 cence. These fluorescytes normally 

 constitute only 0.1% of the red cells 

 (Keller, Ch. J. and K. A. Seggel, Folia 

 Haematol, 52, 241, 1934). No paral- 

 lellism was found to exist between the 

 reticulocytosis in cases of remission of 

 pernicious anemia and the concentra- 

 tion of porphyrin in the erythrocytes, 

 which reaches a ma.ximum after the 

 reticulocyte peak. Watson, Grinstein, 

 and Hawkinson have confirmed this 

 latter observation (J. Clin. Invest., 

 1944, 23, 69-80). A very comprehen- 

 sive review describing the distribution 

 of porphyrins in the human body ap- 

 peared in a book by Lemberg and 

 Legge, "Hematin Compounds and Bile 

 Pigments" (Interscience Publishers, 

 1949). 



Minute quantities of porphyrins may 

 be detected in tissues or solutions by 

 virtue of the red fluorescence of these 

 substances when they are examined in 

 near ultraviolet light (Wood's light). 

 Konigsdorfer, Borst, and Fischer em- 

 ployed a spectral analysis microscope 

 to detect and identify porphyrins in 

 histological material (See Fischer and 

 Orth's Die Chemie des Pyrrols, 1937, 

 press of Paul Dunhaupt, Kothen. It is 

 also available in Lithoprint form: Ed- 

 wards Bros., Ann Arbor, Mich.). At- 

 tempts have been made, Kliiver, H., 

 Science, 1944, 99, 482-484, to identify 

 the type of porphyrin present in tissues 

 and in nervous tissue by means of 

 fluorescence spectra determination. 

 The precise identification and deter- 

 mination of porphyrins involves deter- 

 mination of relative solubility in ether 

 and in acid solutions of various concen- 

 trations, absorption spectra, and melt- 

 ing points of the methylesters. 



The detection of porphj^rins in tissues 

 by means of the visually observed red 

 fluorescence is beset with several pit- 

 falls. Red fluorescence is not a specific 

 test, because occasionally other nat- 

 urally occurring red fluorescent sub- 

 stances are encountered. The red 

 fluorescence of porphyrins may also be 

 masked in at least two ways: 



1. The presence of certain substances 

 which quench the fluorescence of the 

 porphyrin, i.e., protoporphyrin and 

 coproporphyrin are abundant in bone 

 marrow, but the fluoresence is not ap- 

 parent because of the high concentra- 

 tion of heme compounds and other 

 forms of iron. 



2. The presence of a substance or sub- 

 stances with a blue-green or in other 

 words, a complimentary fluorescence 

 spectrum. As one would expect, por- 

 phyrin in such a combination gives rise 



to a white fluorescence, i.e., urine us- 

 ually contains substances which flu- 

 oresce blue-green. The addition of 

 porphyrin changes this to white fluores- 

 cent urine. Urine fluoresces red only 

 when the concentration of porphyrin is 

 very high. 



For an excellent account of the chem- 

 istry and distribution of porphyrins in 

 tissues and organs, the reader is referred 

 to the review of Dobriner, K., and 

 Rhoads, C. P., Physiol. Rev., 1940, 20, 

 416-468. Everett's Medical Biochem- 

 istry (1942, Paul B. Hoeber, New York) 

 also contains a good summary of this 

 field. In the following discussion, some 

 of the original references to statements 

 regarding porphyrins have been 

 omitted. These may be found in one 

 of the above reviews or in Fischer and 

 Orth. Most of the porphyrins en- 

 countered in nature may be classified 

 as type III or type I of the four series 

 of isomers. This is because proto- 

 porphyrin, which belongs to the type 

 III series, is involved in the formation 

 of such important substances as chloro- 

 phyl, hemoglobin, myoglobin, cyto- 

 chromes, catalase, peroxidase, and 

 cytochrome oxidase. Protoporphyrin 

 (and a small amount of coproporphyrin) 

 are usually formed during the synthesis, 

 but as a general rule, porphyrin is not 

 formed during the breakdown of these 

 compounds in the liver. 



Intestinal bacteria convert many of 

 these heme compounds to protopor- 

 phyrin. Deuteroporphyrin, copropor- 

 Ehyrin III, and mesoporphyrin may all 

 e derived from this. These same por- 

 phyrins may also result from the sterile 

 autolysis of hemoglobin or myoglobin 

 (Hoagland, R., J. Agr. Res., 1916, 7, 

 41-45). It is, therefore, probable that 

 these pigments would be present in 

 thrombotic areas, severely damaged 

 tissues, and necrotic tissues in general. 

 Hematoporphyrin is an artificial por- 

 phyrin resulting from the treatment of 

 reduced hemoglobin with strong acids. 

 Since it does not occur in nature, the 

 name is unfortunate and has given rise 

 to much confusion (see "Hematopor- 

 phyrin"). 



Normally 20-100 micrograms of co- 

 proporphyrin I are excreted daily in the 

 urine. Coproporphj'rin, as its name 

 implies, is present in large amounts in 

 the feces, but is also found in the am- 

 niotic fluid, meconium, and in the 

 sebaceous glands in certain areas of the 

 skin of the human subject (Fischer- 

 Orth; Figge, Symposium on Cancer, 

 A. A. A. S., 1945, 117-128). In certain 

 pathological states, large amounts of 

 the ether insoluble uroporphyrins are 



