Butyl paraben and propyl paraben modulate bisphenol A and estradiol concentrations in female and male mice

People are routinely exposed to the antimicrobial preservatives butyl paraben (BP) and propyl paraben (PP), as well as the monomer of polycarbonate plastics, bisphenol A (BPA). These chemicals are reliably detected in human urine and potentially interact. We investigated whether BP or PP exposure can modulate the concentrations of ¹⁴C-BPA and 17β-estradiol (E₂). Female and male CF1 mice were each given a subcutaneous injection of oil containing 0 (vehicle), 1, 3, or 9mg BP or PP, then given a dietary supplement containing 50μg/kg ¹⁴C-BPA. Radioactivity was measured in tissues through liquid scintillation counting. Significantly elevated ¹⁴C-BPA concentrations were observed following BP treatment in blood serum of both sexes, as well as the lungs, uterus, and ovaries of females and the testes and epididymides of males. Treatment with PP significantly elevated ¹⁴C-BPA concentrations in the uterus only. In another experiment, female and male CF1 mice were each injected with vehicle, 3mg BP, or 3mg PP, and E₂ was measured in urine 2-12h later. Whereas PP did not affect E₂, BP significantly elevated E₂ 6-10h after injection in females and 8h after injection in males. These data indicate that BP and PP can alter the pharmacokinetics of BPA in vivo, and that BP can modulate E₂ concentrations. These results are consistent with evidence that parabens inhibit enzymes that are critical for BPA and E₂ metabolism, and demonstrate the importance of considering concurrent exposure to multiple chemicals when determining regulatory exposure limits.