Effect of constant light on DMBA mammary tumorigenesis in rats

A study of light, and mammary tumorigenesis was conducted in rats. One-hundred female Sprague-Dawley rats were divided by weight into two groups. One group was exposed to constant light (LL) from 26 days of age, and the second group was exposed to 8 h light and 16 h dark per day (LD). Both groups re...

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Bibliographic Details
Published in:Cancer letters 2000-02, Vol.148 (2), p.121-126
Main Authors: ANDERSON, L. E, MORRIS, J. E, SASSER, L. B, STEVENS, R. G
Format: Article
Language:English
Subjects:
9,10-Dimethyl-1,2-benzanthracene
Animals
Biological and medical sciences
Carcinogenesis, carcinogens and anticarcinogens
Carcinogens
Circadian Rhythm
Cocarcinogenesis
Darkness
Female
Light
Mammary Glands, Animal - drug effects
Mammary Glands, Animal - growth & development
Mammary Neoplasms, Experimental - chemically induced
Mammary Neoplasms, Experimental - etiology
Mammary Neoplasms, Experimental - pathology
Medical sciences
Physical agents
Rats
Rats, Sprague-Dawley
Tumors
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Summary:A study of light, and mammary tumorigenesis was conducted in rats. One-hundred female Sprague-Dawley rats were divided by weight into two groups. One group was exposed to constant light (LL) from 26 days of age, and the second group was exposed to 8 h light and 16 h dark per day (LD). Both groups received an 8 mg dose of a chemical carcinogen, dimethylben-zanthracene (DMBA) at 52 days of age. At 13 weeks post-DMBA, there were significantly fewer mammary tumors in the LL group compared with the LD group. Constant light was clearly demonstrated to have a profound effect on mammary tissue development. Although virgin, the majority of the LL rats (29/50) had gross evidence of lactation at 141 days of age. None of the LD rats (0/50) showed evidence of milk production. These results suggest that constant light not only substantially accelerated mammary gland development, but pushed development of the tissue past the stage normally observed in virgin animals (to the lactation stage).
ISSN:0304-3835
1872-7980
DOI:10.1016/S0304-3835(99)00320-1