594 5. QUINONES 



However, many different skin reactions occur following exposure to the 

 phenylenediamines; some are probably attributable to a sensitization, 

 which Mayer (1948) related to the ability of p-quinoneimine and p-qui- 

 nonediimine to react with the SH and amino groups of skin proteins. He 

 pointed out that 2,5-diamino-p-xylene, which can be oxidized to the qui- 

 nonediimine but would not react readily with these protein groups, is not 

 a sensitizer. A correlation between epithelial sensitization and carcinoge- 

 nicity was suggested. 



An interesting reaction to p-phenylenediamine is the rapid development 

 of facial and neck edema (Hanzlik, 1923 a). m-Phenylenediamine does 

 not produce this although it causes some pulmonary edema. o-Phenylene- 

 diamine is even less potent (Tainter et al., 1929). Edematous swelling of 

 the neck muscles and skin, the tongue, and the larynx reaches a maximum 

 in around 2 hr after administration, but can be seen as early as 15 min after 

 injection (Fuchs, 1963). The tongue capillaries show separation and re- 

 duction of the endothelial cells, osmiophilic thickening of the ground 

 substance, and sections in which the flow no longer occurs. Numerous small 

 vacuoles appear in the capillary endothelial cell cytoplasm and pathological 

 changes are observable in the mitochondria and nuclei. Death of the animal 

 may result from the asphyxia brought about by the swelling. Such a 

 remarlcable selectivity of action on certain capillary beds (assuming that 

 the direct action is indeed on the capillaries) is unique among enzyme 

 inhibitors or SH reagents, and it would be most interesting to determine 

 whether this action has a metabolic basis. It is not evident with the benzo- 

 quinones, so that it is not justifiable at the present time to relate the 

 edema to a quinonoid structure. 



