Short-time exposure to vinclozolin in utero induces testicular maldescent associated with a spinal nucleus alteration of the genitofemoral nerve in rats

Abstract

Background/purpose Vinclozolin (V), a known antiandrogen, has been used widely to protect fruits, vegetables, and turf from fungus damage. The aim of this study was to clarify the effect of V on both the development of the spinal cord nucleus and testicular descent in rats. Methods Pregnant rats were administered 200 mg/kg/d of V from day 16 to 18 of gestation. At 5 days of age, the genitofemoral nerve (GFN) of male pups was identified on the psoas muscle, and diamidinophenyl indole was applied to the proximal cut end of the GFN. Forty-eight hours later, the T11 to L4 level of the spinal cord was removed, and 30-μm frozen serial sections were made. Next, the spinal nuclei labeled in a retrograde fashion by diamidinophenyl indole (DAPI) were examined with a fluorescence microscope. Additional male pups survived until 60 days of age to evaluate the position of the testes. Results The size of the DAPI-labeled spinal nuclei were smaller in the V-treated rats than in the control rats. The average number of the DAPI-labeled spinal nuclei decreased significantly more in the V-treated rats (176+/−33) than in the controls (247+/− 21; P < .05) during the newborn period. At 60 days of age, 15 of the 26 male rats showed either unilateral or bilateral undescended testes in the V-treated rats. The incidence of cryptorchidism was also significantly higher in the V-treated rats (57.7%) than in the controls (0%; P < .05). Conclusions The antiandrogenic effect of the prenatal administration of V inhibited the development of the GFN nucleus in the spinal cord and induced testicular maldescent in rats. These results support the hypothesis that androgens regulate the descent of the testis through GFN development.