RESUMO
<p><b>OBJECTIVE</b>To study the mechanism of dichlorvos leading to hypospadia of rats.</p><p><b>METHODS</b>From the 12th to the 17th day of conception, 20 pregnant female rats (the experiment group) were given 10 mg/(kg x d) dichlorvos, while another 10 (the control group) administered 1.5 ml 0.9% NaCl/day. Out of 88 male newborns of the 20 experimental mother rats, 22 had hypospadia, while out of the 33 male newborns of the 10 controls, none had the problem. Five hypospadia newborns from the experiment group and another 5 normal ones from the control group were raised to sexual maturity, and then their testes were excised and embedded in paraffin, and the tissue sections were analyzed by regular HE staining and SP immunohistochemical staining with Calretinin.</p><p><b>RESULTS</b>HE staining showed that the number of Leydig cells in the testis tissues of the hypospadia rats decreased significantly compared with the normal ones, but no change was observed either in the number or in the morphology of the seminiferous tubules. Moreover, the Calretinin positive Leydig cells were reduced dramatically in the testes of the hypospadia rats.</p><p><b>CONCLUSION</b>Pregnant female rats, when exposed to dichlorvos, may cause reduction of testis Leydig cells in their male offsprings. Thus the probable mechanism of rat hypospadia induced by dichlorvos may lie in the decrease of the testosterone level caused by damage to Leydig cells from dichlorvos toxicity.</p>