Molecular and toxicologic research in newborn hypospadiac male rats following in utero exposure to di-n-butyl phthalate (DBP).

The objective of this study was to first evaluate the developmental abnormalities and carry out the molecular analysis of external genitalia in newborn hypospadiac male rats induced by maternal exposure to di-n-butyl phthalate (DBP). Timed-pregnant rats were given DBP by gastric intubation at dose of 750 mg/kg body weight (bw)/day from gestation day (GD) 14 to GD18 to establish a hypospadiac rat model. The incidence of hypospadias was 46.67% in male offsprings. On postnatal day (PND) 7, at the newborn stage, decreased body weight and anogenital distance (AGD)/body weight ratio were observed in newborn hypospadiac male rats. The general image and transverse serial histological analysis of genitalia of newborn hypospadiac male rats confirmed the malformation. Autopsy analysis revealed development of reproductive organs (testes, genital tubercle (GT)), hollow organs (stomach, bladder), and solid organs (brain, heart, liver, spleen, lung, kidney, pancreas) in newborn hypospadiac male rats affected by DBP. Moreover, significantly decreased gene expression of important signaling molecules necessary for GT formation including sonic hedgehog signaling molecules (Shh and Ptched 1), bone morphogenetic proteins signaling molecules (Bmp4 and Bmp7), fibroblast growth factor signaling molecules (Fgf8, Fgf10 and Fgfr2), and the transforming growth factor-beta superfamily signaling molecules (TGF-beta1 and TGF-beta receptor III) were observed, for the first time, in the GT of newborn hypospadias induced by DBP. These results showed that the reproductive system and development conditions of newborn hypospadiac rats were damaged by DBP. These disturbed signaling pathways which orchestrating genital development might play an important role in the toxic process of DBP induced hypospadias.