Effect of internal emitters on liver tumours induced by dimethylaminoazobenzene.

TUMOURS may be induced in rodents by radiation or by chemical treatment. Few examinations have sought to investigate possible interrelationships between radiation and chemical carcinogenesis. In the few investigations reported, external radiations have been used. Shubik et al.1 found that croton oil induced tumours in mouse skin that had been irradiated with 204T1, although neither treatment alone resulted in tumour formation. Methyl-cholanthrene and β-irradiation were reported as approximately additive in their carcinogenic action on mouse skin2. Shay et al.3 reported that X-irradiation promoted the effectiveness of methylcholanthrene as a mammary carcinogen. In contrast, Yokoi4 found X- and β-irradiation caused degeneration of benzpyrene-induced tumours in mice.