An investigation of systemic exposure to bisphenol AF during critical periods of development in the rat.

Due to structural similarity to bisphenol A and lack of safety data, the National Toxicology Program (NTP) is evaluating the potential toxicity of bisphenol AF (BPAF) in rodent models. The current investigation reports the internal exposure data for free (unconjugated BPAF) and total (free and conjugated forms) BPAF during critical stages of development following perinatal dietary exposure in Hsd:Sprague Dawley®SD® rats to 0 (vehicle control), 338, 1125, and 3750 ppm BPAF from gestation day (GD) 6 to postnatal day (PND) 28. Free and total BPAF concentrations in maternal plasma at GD 18, PND 4, and PND 28 increased with the exposure concentration; free BPAF concentrations were ≤ 1.61% those of total BPAF demonstrating extensive first pass metabolism of BPAF following dietary exposure in adults. Free and total BPAF were quantified in GD 18 fetuses and PND 4 pups with free concentrations 11.7-53.4% that of corresponding total concentrations. In addition, free concentrations were higher (130-571%) and total concentrations were lower (1.71-7.23%) than corresponding concentrations in dams, demonstrating either preferential transfer of free BPAF and/or inability of fetuses and pups to conjugate BPAF. Free and total concentrations in PND 28 pups were similar to maternal concentrations demonstrating direct exposure of pups via feed and that conjugating enzymes are developed in PND 28 pups. In conclusion, these data demonstrate considerable gestational and lactational transfer of parent aglycone from the mother to offspring. Since the ontogeny of conjugating enzymes in humans is similar to that of rodents, the data from rodent BPAF studies may be useful in predicting human risk from exposure to BPAF.

Toxicokinetics and bioavailability of bisphenol AF following oral administration in rodents: A dose, species, and sex comparison.

We investigated the toxicokinetics and bioavailability of bisphenol AF (BPAF) in male and female Harlan Sprague Dawley rats and B6C3F1/N mice following a single gavage administration of 34, 110, or 340 mg/kg. A validated analytical method was used to quantitate free (unconjugated parent) and total (unconjugated and conjugated) BPAF in plasma. BPAF was rapidly absorbed in rats with the maximum plasma concentration, Cmax, of free BPAF reached at ≤2.20 h. BPAF was cleared rapidly with a plasma elimination half-life of ≤3.35 h. Cmax and the area under the concentration versus time curve, AUC0-∞, increased proportionally to the dose. Total BPAF Cmax was reached ≤1.07 h in rats with both Cmax (≥27-fold) and AUC0-∞ (≥52-fold) much higher than corresponding free values demonstrating rapid and extensive conjugation of BPAF following oral administration. Absorption of BPAF following a 34 mg/kg gavage dose in mice was more rapid than in rats with free BPAF Cmax reached ≤0.455 h. Free BPAF was cleared rapidly in mice with an elimination half-life of ≤4.22 h. Similar to rats, total BPAF was much higher than corresponding free BPAF. There was no apparent sex-related effect in plasma toxicokinetic parameters of free or total BPAF in mice and rats. Bioavailability in rats was ~ 1% with no apparent dose-related effect. Bioavailability in mice was slightly higher than in rats (male ~ 6%, female 3%). These data demonstrate that BPAF was rapidly absorbed following gavage administration in rodents, rapidly and extensively conjugated with low bioavailability.