Plasma concentration and placental transfer of bromofenofos in rats

Bromofenofos (BF) was administered by gavage once to non-pregnant and pregnant rats at 50 mg/kg and the plasma concentration-time curves of BF and its metabolite dephosphate bromofenofos (DBF) were determined by high-performance liquid chromatography. DBF reached a peak at 9 h, with 113.4 +/- 5.2 micrograms/ml, followed by a subsequent decline with a plasma half-life of approximately 24 h, but BF was not detected at any time. Next, the concentration of DBF in the conceptus was determined in rats administered BF (50 mg/kg) on day 10 of pregnancy. The concentration in the conceptus did not exceed 30% of that in the maternal plasma at all times, with a maximum of 32.3 +/- 3.3 micrograms/g at 12 h. No BF was detected in maternal plasma. Third, BF (50 mg/kg) was administered to rats on day 15 of pregnancy to determine whether DBF could cross the placenta. The concentration of DBF in the placenta was nearly half that in the maternal plasma at all times. The fetal concentration was approximately 20% of the concentration in the maternal plasma by 24 h. DBF was detected in the amniotic fluid at all times, but the concentration was low, with a maximum of 11.1 +/- 1.4 micrograms/ml at 12 h.