PONTACYL CARMINE 6B 



199 



PORPHYRINS 



bluish fuchsia darkened by mordanting 

 with potassium bichromate. Not im- 

 portant in microtechnique (Emig, 

 p. oG). 



Pontacyi Carmine 2 G (CI, 31)— Made by 

 DuPont. Light fastness 3. More in- 

 tense color than azofuchsin. Action on 

 fungous mycelia (Emig, p. 29). 



Pontamine Fast Pink BL (CI, 353), a disazo 

 direct dye of light fastness 3 to 4. Use 

 in acid and alkaline solutions as stain 

 for plant tissues and algae are described 

 (Emig, p. 39). 



Pontamine Sky Blue 5BX, see Niagara Blue 

 4B. Use in measurement of lymph flow 

 (McMaster, P. D., J. Exper. Med., 1937, 

 ()5, 373-392). 



Poppy Seed Oil, reactions in tissue to fat 

 stains after various fixations (Black, 

 C. E., J. Lab. & Clin. Med., 1937-38, 

 23, 1027-1036). 



Porphyrins.— Written by Frank H. J.Figge, 

 Dept. of Anatomy, University of Mary- 

 land Medical ISchool, Baltimore, Md. 

 1916— There is no specific histo-chemical 

 reaction for porphyrins, but Watson, 

 C. J. and Clark, W. O., Proc. Soc. 

 Exp. Biol. & Med., 1937, 36, 65-70 be- 

 lieve that it is the protoporphyrin in 

 reticulocytes that stains with brilliant 

 cresyl blue. They have demonstrated 

 that this dye and protoporphyrin are 

 mutual precipitants (see Reticulocytes) . 

 Minute quantities of porphyrins may be 

 detected in tissues or solutions by vir- 

 tue 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 Chemic des Pyrrols, 1937, 

 press of Paul Dunhaupt, Kothen. It is 

 also available in Lithoprint form: Ed- 

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

 tem^pts 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 porphyrins 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 substanecs 



which quench the fluorescence of the 

 porphyrin, i.e., protoporphyrin and 

 coproporphyrin are abundant in bone 

 marrow, but the fluorescnce 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 chein- 

 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- 

 phyrin III, and mesoporphyrin may all 

 be 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"). 



