Nonylphenol ethoxylates, but not nonylphenol, are substrates of the human multidrug resistance P-glycoprotein.

Alkylphenol ethoxylates are surfactants that are commonly used in industry and in home care products. They are broken down by anaerobes to yield toxic environmental pollutants such as nonylphenol. In this study, we tested whether nonylphenol ethoxylates and their most common biodegradation product, nonylphenol, were substrates of human P-glycoprotein. In vivo and in vitro assays showed that the enzyme interacts with a wide variety of nonylphenol ethoxylate compounds, but not with nonylphenol. These results suggest that P-glycoprotein can protect organisms from the toxic and estrogenic effects of nonylphenol ethoxylates, but not from the major biodegradation product, nonylphenol.