Effects of dietary fat and alpha-tocopherol on gamma-glutamyltranspeptidase activity of 7, 12-dimethylbenz(alpha)anthracene-induced mammary gland adenocarcinomas.
The levels of gamma-glutamyltranspeptidase (GGTP) (EC 2.3.2.2) were measured in 7, 12-dimethylbenz(alpha)anthracene-induced mammary adenocarcinomas, in control mammary gland tissue and in sera from tumor-bearing and control rats. The carcinogenic process was modulated by diets differing in the type and amount of fat with and without alpha-tocopherol supplementation. Rat mammary adenocarcinomas showed significantly elevated (up to 25-fold) levels of GGTP when compared with adjacent histologically-uninvolved tissue or with mammary tissue of control rats. GGTP activity in sera from tumor-bearing rats was also elevated up to 4-fold than in the corresponding controls. Histochemical studies of the frozen section of mammary adenocarcinomas indicated that GGTP was localized in neoplastic ductal epithelial cells. In tumor rats on alpha-tocopherol supplemented diets, GGTP activity in the adenocarcinomas was mainly in the particulate (membrane-bound) fraction. In contrast, the tumor rats receiving alpha-tocopherol-deficient diets, the total GGTP activity was distributed in both particulate and cytosolic fractions, suggesting an altered membrane-GGTP interaction. The levels of GGTP in control mammary gland and sera of control rats from the low fat dietary groups were up to 7-fold higher than the corresponding control values in either of two high-fat groups. These high levels of GGTP in the serum and tissues of animals from the low fat dietary group are consistent with lower tumor incidence through enhanced carcinogen detoxification.
D015127:9,10-Dimethyl-1,2-benzanthracene; D000230:Adenocarcinoma / Q000139:chemically induced / Q000201:enzymology*; D000818:Animals; D004041:Dietary Fats / Q000494:pharmacology*; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000201:enzymology*; D051381:Rats; D014810:Vitamin E / Q000494:pharmacology*; D005723:gamma-Glutamyltransferase / Q000097:blood / Q000378:metabolism*
D004041:Dietary Fats; D014810:Vitamin E; D015127:9,10-Dimethyl-1,2-benzanthracene; D005723:gamma-Glutamyltransferase