Investigating compensation and recovery of fathead minnow (Pimephales promelas) exposed to 17α-ethynylestradiol with metabolite profiling

H-1 NMR spectroscopy was used to profile metabolite changes in the livers of fathead minnows (Pimephales promelas) exposed to the synthetic estrogen 17 alpha-ethynylestradiol (EE2) via a continuous flow water exposure. Fish were exposed to either 10 or 100 ng EE2/L for 8 days, followed by an 8 day depuration phase. Livers were collected after days 1, 4, and 8 of the exposure, and at the end of the depuration phase. Analysis of polar extracts of the liver revealed a greater impact of EE2 on males than females, with metabolite profiles of the former assuming similarities with those of the females (i.e., feminization) early in the exposure. Biochemical effects observed in the males included changes in metabolites relating to energetics (e.g., glycogen, glucose, and lactate) and liver toxicity (creatine and bile acids). In addition, amino acids associated with vitellogenin (VTG) synthesis increased in livers of EE2-exposed males, a finding consistent with increased plasma concentrations of the lipoprotein in the fish. Using partial least-squares discriminant analysis (PLS-DA), the response trajectories of the males at both exposure concentrations were compared. This revealed an apparent ability of the fish to compensate for the presence of EE2 later in the exposure, and to partially recover from its effects after the chemical was removed.