Null effects of vitamin A analogs on the dimethylnitrosamine kidney tumor model

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Abstract
The effect of retinoids on the induction of both epithelial and mesenchymal tumors of the rat kidney by a single dose of 40 mg/kg dimethyinitrosamine was tested using 13- cis -retinoic acid and the trimethyimethoxy phenyl analog of retinoic acid ethylamide. 13- cis -retinoic add was administered for 3 weeks, 10 weeks, or 26 weeks, post-carcinogen treatment, in order to coincide with known morphological phases occurring within the kidney which culminated in the development of macroscopic tumors. The ethylamide analog and placebo beadlets were administered for the 26 week period only. None of the retinoid schedules significantly influenced the survival of the animals, nor the incidences of renal mesenchymal tumors or renal cell adenomas/adenocarcinomas. Tumor latency, histological grade or frequency of metastatic invasion were also unaltered by the treatments. Possible reasons for the observed lack of effect are discussed, including speculation regarding the potency of this single-dose model of chemical carcinogenesis.