Bioavailability and mammary excretion of bisphenol A in Sprague-Dawley rats

This study reports the absolute oral bioavailability and mammary excretion of bisphenol A in rats. The oral bioavailability was determined after admin istration of relatively low iv (0.1 mg/kg) and oral (10 mg/kg) doses of bis phenol A to rats. After iv injection, serum levels of bisphenol A declined biexponentially, with the mean initial distribution and terminal eliminatio n half-lives being 6.1 +/- 1.3 min and 52.5 +/- 2.4 min, respectively. The systemic clearance (Cl-s) and the steady-state volume of distribution (V-ss ) averaged 107.9 +/- 28.7 ml/min/kg and 5.6 +/- 2.4 L/kg, respectively. Upo n oral administration, the maximum serum concentration (C-max) and the time to reach the maximum concentration (T-max) were 14.7 +/- 10.9 ng/ml and 0. 2 +/- 0.2 h, respectively. The apparent terminal elimination half-life of b isphenol A (21.3 +/- 7.4 h) after oral administration was significantly lon ger than that after iv injection, indicating the flip-flop of the absorptio n and elimination rates. The absolute oral bioavailability of bisphenol A w as low (5.3 +/- 2.1%). To determine the extent of mammary excretion, bisphe nol A was given by simultaneous iv bolus injection plus infusion to steady state at low, medium, and high doses. The steady-state serum levels of bisp henol A were linearly increased with higher dosing rates. The systemic clea rance (mean range, 119.2-154.1 ml/min/kg) remained unaltered over the dosin g rate studied. The levels of bisphenol A in milk exceeded those in serum, with the steady-state milk to serum concentration ratio being 2.4-2.7.