600 XII. HEMOGLOBIN CATABOLISM, II 



are exposed to sunlight or ultraviolet light, the skin is locally destroyed 

 and death in shock may result. This photosensitizing action of por- 

 phyrins was discovered by Hausmann {1179,1180). A number of 

 reviews on this subject are available (294,322,662,1070,1181,1182, cf. 

 also 295,296). This dangerous action of porphyrins was also demon- 

 strated in a self-experiment by Meyer-Betz {1931). Gaffron {9G6), 

 Harris {1132), and Smetana {2575) showed that it consists in a 

 photoxidation of proteins in the skin {cf. also 324,1351), while 

 Thomas {2798) demonstrated the destruction of enzyme systems by 

 photoxidation. Comparatively long-wave ultraviolet radiation of 

 about 400-mM wavelength is most effective. All these experiments 

 were carried out with hematoporphyrin, but the photosensitizing 

 action of physiologically important porphyrins on white mice was 

 studied by Fischer and Zerweck {891). Uroporphyrin I was strongly 

 active, coproporphyria somewhat less, and proto- and hematopor- 

 phyrins only slightly; in man no sensitization by protoporphyrin has 

 been found {875). Bingel {cf. 1914) found uroporphyrin III inactive 

 in contradistinction to uroporphyrin I, and coproporphyrin III less 

 active than coproporphyrin I. The embryo, in which uroporphyrin 

 occurs, is not exposed to light, while the fox squirrel, in which it 

 occurs physiologically, is protected against photosensitization by its 

 black fur. Serum was observed to afford protection against photo- 

 sensitization in vitro {2212,25^6) but only with coproporphyrin, not 

 with uroporphyrin (Gildemeister, 1000). It is not yet quite clear 

 whether the lack of the photosensitization in acute porphyria is due 

 to the smaller activity of uroporphyrin III or to the presence of the 

 porphyrin in the body as an inactive, colorless precursor. Porphyrin 

 formed from chlorophyll in the gastrointestinal tract of sheep has 

 been found to be the cause of some animal diseases accompanied by 

 photosensitization {U5,U6,519,2196,2256,2273). 



3.5.2. Other Toxic Actions. The symptoms of acute porphyria 

 and perhaps also of lead poisoning (Schreus, 2464) are due to different 

 toxic actions of porphyrin, which do not depend on light. Porphyrins 

 have been found to cause vascular spasms {1025,2212,2348,2469,2707, 

 2850) as well as intestinal spasms {2229,2464,2707,2850). They also 

 probably cause the psychiatric disorders which frequently accompany 

 acute porphyria {406,556,655,1070,1552,2349,2848,2850,2908); Baker 

 and Watson {116) observed pathologic alterations of the myelin 

 sheath in this disease. 



