Dynamics of uptake and elimination of 17α-ethinylestradiol in male goldfish (Carassius auratus)

We used male goldfish (Carassius auratus) as a model species to determine the uptake, elimination, and bioaccumulation of 17α-ethinylestradiol (EE2). Goldfish were exposed to EE2 via two different routes: water (135 ng/L ± 12.8 standard deviation) for 72 h, and food (231 ng/g ± 42 SD) for 120 h. We observed a rapid uptake of EE2 in goldfish, reaching 8.4 ng/g ± 1.2 dry weight (dw) after the first hour of exposure with an uptake rate coefficient (k1) of 45 h−1. The elimination rate coefficient (k2) was determined by a depuration experiment to be 0.0786 h−1. In the feeding experiment, EE2 concentrations increased rapidly, reaching an average of 1.4 ng/g after 3 h following the first dietary exposure with an estimated absorption efficiency (α) of 0.106. An average of 2.66 ng/g ± 0.87 (n = 8) was determined in the 24–72 h samples, whereas EE2 concentrations in fish fell below our method detection limits (0.67 ng/g) for all samples after 72 h, suggesting efficient elimination over time. The bioconcentration factor (BCF) for EE2 reached a maximum of 377, similar to BCFs measured for other pharmaceuticals like fluoxetine and sertraline. Our kinetic data were also used to model various scenarios of EE2 uptake in the aquatic environment. To our knowledge, this is the first report to describe aqueous and dietary EE2 uptake and elimination in fish, as well as providing important data to model EE2 kinetics in fish.

► Goldfish accumulated 17α-ethinylestradiol from aqueous and dietary exposures.
► The EE2 bioconcentration factor (BCF) reached a maximum of 377.
► Absorption efficiency for 17α-ethinylestradiol was 0.106.
► Aqueous uptake supersedes dietary uptake for 17α-ethinylestradiol in fish.