title: Low-fat milk promotes the development of 7,12-dimethylbenz(A)anthracene (DMBA)-induced mammary tumors in rats.
abstract: Commercial cow milk contains considerable amounts of estrogens. Our study assessed the effect of commercial low-fat milk on the development of 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors in rats. Eighty 6-week-old female Sprague-Dawley rats received a single oral dose of 5 mg DMBA. Twenty-four hours later, the animals were divided into 4 groups of 20 animals each and given 1 of 4 test solutions for 20 weeks as their drinking liquid: low-fat (1%) milk (M), artificial milk (A), estrone sulfate solution (0.1 microg/ml, E), or tap water (W). The artificial milk was formulated to supply essentially the same calories as the milk. The low-fat milk contained 378 pg/ml estrone sulfate. Tumor incidence, the cumulative number of tumors and the sum of tumor diameters were higher in the M and E groups than in the A or W groups. Overall, the development of mammary tumors was in the order: M = E > A = W. Whereas the plasma 17beta-estradiol concentration in the M group was the 2nd highest after the E group, the plasma level of insulin-like growth factor (IGF-I) was significantly higher in the M group than in the other 3 groups. In conclusion, commercially available low-fat milk promotes the development of DMBA-induced mammary tumors in rats. The degree of the promotion is almost comparable to that of 0.1 microg/ml estrone sulfate. The high estrogen content in the milk may be responsible for the promotional effects, acting in concert with other hormones such as IGF-I.
authors.affiliation: Deparment of Environmental Health, Medical University of Yamanashi, Tamaho, Yamanashi, Japan.
authors.forename: Li-Qiang
authors.initials: LQ
authors.lastname: Qin
authors.forename: Jia-Ying
authors.initials: JY
authors.lastname: Xu
authors.forename: Pei-Yu
authors.initials: PY
authors.lastname: Wang
authors.forename: Davaasambuu
authors.initials: D
authors.lastname: Ganmaa
authors.forename: Jue
authors.initials: J
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Takashi
authors.initials: T
authors.lastname: Kaneko
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Hoshi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Shirai
authors.forename: Akio
authors.initials: A
authors.lastname: Sato
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D001835:Body Weight; D004435:Eating; D004958:Estradiol / Q000032:analysis / Q000097:blood; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008325:Mammary Neoplasms, Experimental / Q000209:etiology*; D008892:Milk / Q000009:adverse effects* / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004958:Estradiol; D015127:9,10-Dimethyl-1,2-benzanthracene; D007334:Insulin-Like Growth Factor I