The role of high levels of dietary fat in 7,12-dimethylbenzanthracene-induced mouse mammary tumorigenesis: lack of an effect on lipid peroxidation.
The effects of dietary fat on 7,12-dimethylbenzanthracene (DMBA)-induced mammary tumorigenesis were examined in BALB/c female mice. In the first experiment, BALB/c mice were treated with a total dose of 1, 3, or 6 mg DMBA to induce mammary tumors. One week after the last dose of DMBA, the mice were placed on a 5% (LF) or 20% (HF) corn oil semi-purified diet. The 20% corn oil diet resulted in a significantly decreased mean tumor latency period in each of the three groups of mice (p less than 0.05). However, the mammary tumor incidences at 11 months after DMBA treatment were the following: 6 mg DMBA (LF-14/32, HF-17/32); 3 mg DMBA (LF-13/50, HF-14/50); 1 mg (LF-2/50, HF-6/50). In the second experiment, prolonged hormonal stimulation by pituitary isografts, but not a HF diet, enhanced the incidence of mammary tumors in BALB/c mice given a threshold dose of DMBA (0.5 mg). In a further attempt to examine the mechanism of the enhancing effects of dietary fat, lipid peroxidation was measured in the microsomal-mitochondrial fractions of the mammary glands by two assays; measurements of conjugated dienes and TBA reactants (malonyldialdehyde). The high fat diet had no effect on the levels of conjugated dienes in mammary cell membrane preparations and decreased the levels of TBA reactants (malonyldialdehyde). The results indicated that a high fat diet did not lead to enhanced levels of lipid peroxidation in preparations of microsomal mitochondrial membranes from mouse mammary glands. The implications of these results are discussed with respect to the role of dietary fat as a promoter of mouse mammary tumorigenesis.
D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D001835:Body Weight; D003043:Cocarcinogenesis; D004041:Dietary Fats / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006728:Hormones / Q000494:pharmacology; D008054:Lipid Peroxides / Q000378:metabolism*; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced*; D051379:Mice; D008807:Mice, Inbred BALB C
D004041:Dietary Fats; D006728:Hormones; D008054:Lipid Peroxides; D015127:9,10-Dimethyl-1,2-benzanthracene