Reproductive adverse effects of fipronil in Wistar rats

The purpose of the present study was to investigate possible reproductive adverse effects of fipronil (Frontline TopSpot) in female Wistar rats. The pesticide was topically applied to rats (single dose) at different concentrations (70, 140 and 280 mg/kg) and hormonal analysis, estrous cycle, and pregnancy and outcome data were determined. Treatment with fipronil altered cyclicity of female rats lengthening the estrous cycle (days) after a single topic administration of 70 mg/kg (9.7+/-1.18) or 280 mg/kg (14.5+/-1.45) when compared to control (4.8+/-0.17). In the mating study fipronil reduced the pregnancy index (67%) in the highest dose group (280 mg/kg). Plasma progesterone and estradiol levels, obtained in different periods after treatment with fipronil (70 mg/kg), were significantly different 96 h after treatment, when compared to controls. In summary, the results of the present study indicate that fipronil may alter the normal functioning of the endocrine system and cause adverse reproductive effects in female rats.