Abstract
Possible promoting effects of phenylbutazone on carcinogenesis in various organs, including the hematopoietic system and liver, were reinvestigated in inbred female Donryu rats, using wide organ spectrum 2-stage carcinogenesis models. Phenylbutazone was given as a dietary supplement (0.25%) for 24 weeks subsequent to initiation with N-methyl-N-nitrosourea or N-ethyl -N-nitrosourea. No enhancement by phenylbutazone of nitrosourea-induced leukemogenesis was apparent, although a promoting effect was demonstrated, not only for renal and thyroid carcinogenesis as found earlier, but also for hepatocarcinogenesis. On the contrary, an inhibitory effect was shown for intestinal carcinogenesis.
