Normal cycling virgin female Sprague-Dawley rats were divided into different treatment groups and subjected to half ad libitum feed intake for 2 or 4 weeks at consecutive periods of time before and/or after administration of 7,12-dimethylbenz(a)anthracene (DMBA) and then were returned to full-feed. All rats at the end of their respective under-feeding periods showed reductions in serum prolactin and cessation of estrous cycles. However, only rats underfed 1 week prior to and 1 week after DMBA administration showed significant reductions in mammary tumorigenesis for the entire 21 weeks of the experiment when compared to full-fed controls. Rat groups underfed during subsequent weeks after DMBA administration showed no alterations in mammary tumor development as compared to full-fed controls.

These results demonstrate that inhibition and perhaps permanent suppression of mammary tumorigenesis occurred only in rats underfed 1 week before and 1 week after DMBA administration. The inhibitory effects produced by this underfeeding regimen on mammary tumorigenesis may be mediated by suppression of prolactin and estrogen secretion.

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Aided by NIH research Grants CA10771 from the National Cancer Institute, AG00416 from the National Institute on Aging, and AM04784 from the National Institute on Arthritis, Metabolism, and Digestive and Kidney Diseases. Published with the approval of the Michigan Agricultural Experimental Station as Journal Article 10478.

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