In vitro-Ishikawa cell test for assessing tissue-specific chemical effects on human endometrium.

The human endometrium is a fertility-determining factor. Its receptivity during the implantation window may be altered by chemicals. Since human embryo implantation is unique chemical risk assessment cannot be based solely on animal studies. We established a tissue-specific in vitro test based on human endometrial adenocarcinoma (Ishikawa) cells. Progesterone receptor (PR) was selected as primary target gene for estrogenic effects. Changes of mRNA levels were investigated by reverse transcription quantitative real-time PCR. Sigmoidal dose-response curves for up-regulation of PR mRNA and EC(50) values were established for 17beta-estradiol, diethylstilbestrol and the weak xenoestrogen bisphenol A. Nonylphenol also had a clear PR mRNA up-regulating effect. Several other chemicals were characterized as negative compounds. Among them was methoxyacetic acid which may produce false positive results in reporter gene assays. Up-regulation of PR protein by 17beta-estradiol, diethylstilbestrol, bisphenol A and nonylphenol was confirmed by Western Blotting.