Retinol and β‐carotene concentrations in skin, papillomas and carcinomas, liver, and serum of mice fed retinoic acid or β‐carotene to suppress skin tumor formation

Abstract Using 7,12‐dimethylbenz[a] anthracene as the initiator and 12‐O‐tetradecanoyl‐13‐acetate as the tumor promoter on the dorsal skin of Sencar mice, we previously showed that pharmacological dietary all‐trans‐retinoic acid and β‐carotene inhibit the conversion of papillomas to carcinomas in a two‐stage system of chemical carcinogenesis. The purpose of this study was to determine the influence of dietary retinoic acid and β‐carotene on retinoidand β‐carotene concentrations in skin and other tissues. We were unable to measure tissue retinoic acid because of the relatively limited amount of tissue available for analysis and the fast rate of metabolism. Different dietary levels of retinoic acid or β‐carotene did not influence total retinol of skin, papilloma, and carcinoma tissues, which all showed a concentration of approximately 1 ± 0.5 μg/g wet wt. Equally refractory to dietary retinoic acid or β‐carotene was serum retinol concentration. In contrast, dietary retinoic acid protected loss of liver reti...