THE EFFECT OF X-IREADIATION COMPARED TO AN 

 APPARENTLY SPECIFIC EARLY EFFECT OF SKIN 



CARCINOGENSt 



F. DEVIK 



Statens RadiologisJc-Cysiske Laboratorium, Montebello, Oslo, Norway 



An early test for possible skin carcinogens has recently been described by 

 Iversen (1961). He found good correlation between carcinogenic activity and 

 the type of reaction that was recorded after one day by means of a tetra- 

 zolium reduction method (Iversen, 1959). In a blind test of twenty different 

 compounds, the method singled out six carcinogens (e.g. 1.2,5.6-dibenzan- 

 thracene, 3.4-benzpyrene, and others) from the fourteen chemically-related 

 but non-carcinogenic compounds. With the carcinogenic potentialities of 

 X-irradiation in mind, it is of interest to compare the effect of X-irradiation 

 with that of chemical carcinogens recorded by this method. 



The tetrazolium method as applied by Iversen was used to estimate 

 changes in the rate of formazan deposition in the epidermis of hairless mice, 

 following application of different skin irritants. The skin was taken immedi- 

 ately after sacrificing the mice, and incubated for one hour at 37°C in a tetra- 

 zolium solution, with no substrate added. The reduction of tetrazolium salts 

 by living cells is considered to be an indicator of dehydrogenase activities of 

 the ceUs. The formazan formed is insoluble and is deposited in the cells at the 

 site of reduction. The formazan is coloured, and the amount in the epidermis 

 is measured by colorimetric methods. 



The carcinogenic compounds produced an initial rise in formazan 

 deposition on the first day, whereas the non-carcinogenic compounds showed 

 a more or less pronounced depression at the same time (Fig. 1). Iversen has 

 discussed the significance of the test, and considers that the increased deposi- 

 tion of formazan signifies a disturbance in the function of the mitochondria, 

 with release of enzymes (Iversen and Evensen, 1962). 



In collaborative work with Iversen, the effect of local X-irradiation on the 

 epidermis of the same strain of mice has been tested in the same way as for 

 the carcinogens, using X-ray doses ranging from 500 to 2,700 r (Iversen and 

 Devik, 1962). A gradual increase in formazan deposition was observed, which 

 was more pronounced the higher the dose, but more delayed in time when 



t Work performed at Statens radiologisk-fysiske laboratorium, Montebello, Oslo, and 

 Institutt for Generell og Eksperimentell Patologi, Rikshospitalet, Oslo. 



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