Effects of low-dose subchronic exposure to the phenylpyrazole insecticide fipronil in juvenile mice

Fipronil (FPN) inhibits gamma-aminobutyric acid type A receptors and exhibits strong insecticidal effects. Although FPN’s adverse effects on mammals have been reported recently, few studies have examined subchronic exposure to low doses. We orally administered FPN (0.43 mg/kg) to 4-week-old male mice for 6 wk and assessed their behavior and blood characteristics. Compared with the control group, the FPN-treated group presented reduced weight gain but upward trends in locomotor activity and blood histamine levels. Fipronil sulfone (FPNS) was detected in all individuals, whereas FPN was not detected in any individual. The present study shows for the first time that subchronic exposure to low-dose FPN in mice led to FPNS conversion in the body, affecting weight gain and behavior.