Application of the yeast-based reporter gene bioassay for the assessment of estrogenic activity in cow's milk from Poland

Abstract

Milk contain compounds acting through the estrogen receptor signaling. The still open question whether such estrogens pose a risk for human health, encouraged us to measure the overall estrogenic activity of cow's milk in the in vitro yeast reporter bioassay. First, we assessed the ability of the bioassay to detect estrogens frequently detected in milk. The relative potencies of 16 compounds descended in the order: 17β-estradiol (17β-E2), 17α-ethinylestradiol, diethylstilbestrol, dienestrol, 17α-E2, estrone, zearalenone, estriol, equol, genistein, 17β-E2 glucuronide, bisphenol A, apigenin, daidzein. Flavone, 4-n-nonylphenol and 4-t-octylphenol shown no activity in the bioassay.The estrogenic activities of milk samples without hydrolysis were below the detection limit, whereas in 50% of the deconjugated samples they varied between 0.29 and 0.49 ng EEQ mL(-1). We also compared the estrogenic activity in raw cow's milk collected from rural and industrial locations in Poland. In our pilot study we did not observe statistically significant difference in estrogenic activities in milk collected from the two locations. We found that the daily intake of estrogens with milk may be higher than estrogen levels in human serum. Further studies are warranted to evaluate the significance of milk and dairy as a source of estrogens for humans.

Keywords: Cow's milk; Estrogenic activity; In vitro bioassay; Yeast.