Abstract
Groundwater is a reservoir of fresh water. In the goitrous areas the water used for drinking and cooking generally is high in nitrate content. The aim of the present study was to evaluate in that areas, chronic effects to expose of xenopus laevis larvae during a complete metamorphosis process to groundwater. For analyze the effects on thyroid function. The xenopus laevis larvae were divided into 3 work groups submerged, until the end of metamorphosis, in: drinking water as control (C), groundwater as group (G) and drinking water plus potassium perchlorate as positive control (PC). In (G) group metamorphosis process was completed in 37% and 0% in (PC) (p < 0.0001). In the 60 of Niewkoop and Faber, stage the wet weight and body length was in (G) smaller than (C) and (PC) (p < 0.0001). But was not difference in 62 for (G), (PC) was bigger than (C). In 60 stage was no significant differences on the length of the hind limbs. In 62 was bigger in (G) and (PC) than in (C) (p < 0.001). Thyroid hyperplasia was grade 2 in (G) and 3 (PC) (p < 0.001) in 60 stage and 3 in (G) and (PC) in the 62 (p < 0.0001). Follicular hypertrophy and colloid depletion in (G) and (PC) (p < 0.0001). In groundwater was found high nitrates concentrations. These findings suggest that nitrate contaminate groundwater impairs thyroid function of xenopus laevis larvae. These observation could contribute to the current discussion about the acceptable daily intake of nitrate.