Supplementary study of phenylbutazone promoting effects using wide organ spectrum two-stage carcinogenesis models in rats.

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.