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Updated: Aug 18, 2026

Changes in Mammary Gland Morphology and Breast Cancer Risk in Rats
Published on: October 17, 2010
Developmental stages and energy restriction affect cellular oncogene expression in tissues of female rats
1Department of Animal and Range Sciences, North Dakota State University, Fargo 58105.
Abstract:
The influence of developmental stages and energy restriction on c-Ha-ras and c-fos cellular oncogene mRNA level was examined in mammary tissue and liver of female rats. c-Ha-ras and c-fos RNA transcripts in mammary tissue peaked at 9 wk of age, decreased during pregnancy, were lowest at mid-lactation and then increased at 25 wk. c-Ha-ras in liver showed highest expression at 5 wk and was hardly detectable at 11 wk, mid-pregnancy, mid-lactation and 25 wk. Liver c-fos and c-Ha-ras mRNA levels were similar. Lower c-Ha-ras and c-fos mRNA levels were observed in mammary tissue of energy-restricted (to 70% of ad libitum intake) rats at 25 wk compared with those allowed ad libitum access to food. Energy restriction did not affect liver c-Ha-ras and c-fos mRNA levels throughout the experimental period. These results demonstrate that developmental stages and energy restriction affect cellular oncogene mRNA levels with tissue-specific patterns.
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