Effect of moderate vitamin A supplementation and lack of dietary vitamin A on the development of mammary tumors in female rats treated with low carcinogenic dose levels of 7,12-dimethylbenz(a)anthracene.
We examined the effect of moderately increased and of marginal continued dietary supplementation of vitamin A (retinyl acetate) and the effect of lack of dietary vitamin A on the initiation and promotion stages of mammary tumorigenesis in female Sprague-Dawley rats treated with a single low (0.5 mg/100 g body weight) or very low (0.1 mg/100 g body weight) dose of i.v.-administered 7,12-dimethylbenz(a)anthracene. The number of mammary tumors was significantly (P less than 0.05) reduced if prior to and during initiation with 7,12-dimethylbenz(a)anthracene the rats were fed a moderately increased (30 micrograms/day) or marginal (3 micrograms/day) amount of vitamin A, compared to rats fed an adequate (10 micrograms/day) amount of vitamin A. The number of mammary tumors was also significantly (P less than 0.05) reduced when a moderately increased or marginal amount of vitamin A was provided during the tumor promotion phase. In addition, the number of mammary tumors was significantly (P less than 0.05) reduced by the lack of dietary vitamin A during both the initiation and promotion stages of this tumorigenic process, when compared to vitamin A adequate, ad libitum-fed rats, but not when compared to vitamin A adequate, food-restricted controls. The reduction in numbers of mammary tumors observed in these studies was reflected primarily in significant (P less than 0.05) decreases in mammary fibroadenomas; the number of mammary carcinomas was often reduced, but due to a low frequency of the carcinomatous lesions, this reduction did not reach the 5% level of statistical probability. Plasma and liver vitamin A levels were determined during both the initiation and promotion stages. As the dietary supplementation of vitamin A increased from 0 to 30 micrograms/day, there was an increase in mean liver and plasma vitamin A levels. No consistent correlation between plasma and liver vitamin A levels and the occurrence of mammary tumors was observed, except with the moderately increased (30 micrograms/day) intake of vitamin A, that resulted in a small, but statistically significant (P less than 0.05) increase of serum retinol at initiation; this may account for the observed reduction in mammary tumors. These results provide evidence that moderate alterations in vitamin A consumption can modulate low-dose chemically induced mammary gland tumorigenesis. Most importantly, suppression of mammary gland tumorigenesis can be achieved by moderately increased, frequent, and regular consumption of vitamin A; prolonged consumption of vitamin A-deficient diets or diets marginal in vitamin A does not enhance the risk of mammary tumor development.
D015127:9,10-Dimethyl-1,2-benzanthracene; D000230:Adenocarcinoma / Q000139:chemically induced / Q000209:etiology / Q000517:prevention & control; D000232:Adenofibroma / Q000139:chemically induced / Q000209:etiology / Q000517:prevention & control; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D008099:Liver / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000209:etiology* / Q000517:prevention & control; D051381:Rats; D014801:Vitamin A / Q000008:administration & dosage* / Q000378:metabolism; D014802:Vitamin A Deficiency / Q000150:complications*
D014801:Vitamin A; D015127:9,10-Dimethyl-1,2-benzanthracene