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Short-Term Exposure to Trifluralin in the In Vivo Rat Model
Citation:
HEDGE, J. M., K. B. PAUL, AND K. M. CROFTON. Short-Term Exposure to Trifluralin in the In Vivo Rat Model. Presented at Annual Meeting of the Society of Toxicology, Baltimore, MD, March 15 - 19, 2009.
Impact/Purpose:
This work confirms that short-term exposure to trifluralin disrupts thyroid hormone homeostatis in rats.
Description:
Trifluralin is a selective, preemergence 2,6-dinitroaniline herbicide used to control many annual grasses and broadleaf weeds. Human exposure is likely to occur via consumption of vegetables and fruit and possibly fish from trifluralin run off in water. It has previously been reported that trifluralin causes thyroid follicular cell tumors in rats from chronic feeding studies. Recently trifluralin was shown to reduce thyroxine (T4) by upregulating select hepatic UGT isozymes following a 2 week exposure. In order to generate baseline data for use in future mixtures studies we examined whether moderate to low levels of trifluralin would cause any perterbation of thyroid homeostatsis in a short-term (4 day) exposure model. Female Long-Evans rats (26 days old, n=66) were dosed via oral gavage with trifluralin in corn oil vehicle (1ml/kg) at 0, 0.3, 1,3,10, 30, 50 or 300mg/kg/day for 4 consecutive days. Serum and livers were collected 24 hours after the last dose. Body weight gain was not affected by treatment. Liver to body weight ratio was significantly increased with 300mg/kg/day trifluralin (24%). T4 was significantly reduced by 25% only at the 300mg/kg/day dose. This work confirms that short-term exposure to trifluralin disrupts thyroid hormone homeostatis in rats.