Lack of modifying effects of an estrogenic compound atrazine on 7,12-dimethylbenz(a)anthracene-induced ovarian carcinogenesis in rats.

The modifying effects of dietary feeding of atrazine, which is one of the endocrine disrupting chemicals (EDCs), on 7,12-dimethylbenz(a)anthracene (DMBA)-induced ovarian carcinogenesis were investigated in female Sprague-Dawley rats. We also assessed the effect of atrazine on proliferating cell nuclear antigen (PCNA)-index and the expression of estrogen receptor (ER)-alpha and -beta and androgen receptor (AR) in induced neoplasms. Rats were given a single injection of DMBA (0.01 ml of 0.5% DMBA suspended in olive oil) into their left ovary to induce ovarian neoplasms. They also received the experimental diet containing 5, 50 or 500 ppm atrazine for 50 weeks, starting one week after the dosing of DMBA. The diets used were free of soy products. DMBA exposure produced left ovarian adenocarcinoma with an incidence of 45% at the end of the study (week 51). Dietary administration atrazine reduced the incidence of ovarian adenocarcinoma: 22, 28, and 26% incidences in rats fed 5, 50, and 500 ppm atrazine containing diets after DMBA exposure, respectively, without statistical significance among the groups. The PCNA-index in adenocarcinomas was greater than that of surface ovarian epithelium. ER-alpha, beta and AR were expressed in a variable percentage of moderately and poorly differentiated adenocarcinoma cell nuclei, but their reactivity was extremely weak or negative in well differentiated adenocarcinoma cells. These results might suggest dietary feeding of a EDC atrazine did not affect DMBA-induced rat ovarian carcinogenesis. Copyright 2004 Elsevier Ireland Ltd.