الفهرس 
Introduction
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Abstract
The present study investigated the effects of BPA and DEHP on male reproductive tract development. Two separate experiments were carried out on Long- Evans male rats which scarified at age 10, 21, 35 and 90 days postnatally.
The first experiment was designed to describe developmental changes in gene expression in the postnatal testis and epididymis. Tissues were subsequently homogenized and prepared for western blotting analysis. The present study revealed that, there was an age-dependent decrease in GATA-4, Sox9, anti-müllerian hormone (AMH) and estrogen receptor 2 proteins in accordance with their role in sexual development. On other hand, the epididymal AR, ESR1 and Wnt4 protein were greater (P<0.05) in the pre-pubertal period (day 35 post-partum) compared to their levels at 21 and 90 days of age.
The second experiment, Timed-pregnant female rats were exposed to BPA and DEHP by gavage from gestational day 12 to 21. Testes, pituitaries and epididymes were collected at the time of sacrifice. Results showed that prenatal exposure to tested chemicals increased GATA-4, Sox9 and AMH protein in the neonatal rat testis compared to levels in control unexposed animals. Similarly, serum AMH levels was increased with the large dose of both chemicals in adult rat. In addition, prenatal exposure to both BPA and DEHP increased testosterone and 17β-estradiol concentrations in the blood and testis in addition to increase aromatase protein in testis in adult animals.
Pituitary LHβ and FSHβ subunit protein expression was increased in pre-pubertal rats but their levels were decreased in adulthood in treatment groups relative to control. Also, prenatal exposure to these chemicals decreased DNA hydroxymethylation in the adult testis.
Together, the present data suggest that altered developmental programming in the testes associated with chemical exposures are linked to disruption in sexual differentiation events. Results support the view that several adult diseases may have their origin in the fetal period.
The caput epididymis was collected from groups of male offspring at 35 and 90 days of age. The results of the epididymis showed that, the prenatal exposures to both chemicals (BPA and DEHP) modulated protein expression in the developing epididymis, which were evident in the pre-pubertal period and persisted into adulthood. It was interesting to note that BPA, but not DEHP, affected ESR1 and ESR2 protein expression. BPA-induced changes in both AR and ESR expression is significant because a major role in the reabsorption of fluid from within the epididymal lumen was attributed to estrogens. Moreover, estrogen, through activation of ESR-mediated is thought to be involved in the regulation of epididymal contractility and the ejaculatory process in the mature male.
The expression of Wnt4, a member of the Wnt gene family which is known to play a role in sexual differentiation was modulated by chemical exposures. The Wnt4 gene is initially expressed in the indifferent gonad of both sexes but is subsequently downregulated in male. Prenatal exposures to BPA and DEHP increased Wnt4 protein in pre-pubertal male rats while expression was increased only by BPA in adult sexually mature rats. Furthermore, β-Catenin protein in caput epididymis from both pre-pubertal and adult male rats was greater in BPA and DEHP-exposed animals compared to control. This pattern of Wnt4/β-Catenin protein in chemical-exposed animals appears related to the female phenotype, i.e., high expression levels early in development continued into the postnatal period unlike a decline that is seen in the male.
Hox gene expression is of particular interest because of its association with segmental development and epididymal function. These results showed that prenatal exposures to BPA, but not DEHP, increased Hoxd4 protein in epididymal tissue from pre-pubertal rats. However, both chemicals caused this effect in the adult epididymis. Hoxa-10 and Hoxa-11 are co-expressed in the reproductive tract and loss of function mutations were known to decrease fertility.
In conclusion, the present data suggested that, the adverse adult effects associated with chemical exposures occurring in the fetal period were related to alter sexual differentiation events that impact gonadotropin subunit expression in pituitary glands and steroid hormone secretion in the testis. In addition, AMH concentrations in serum and expression in testis were affected by exposure to BPA and DEHP. That means AMH may be a biomarker of toxicant activity.
Results also implied that low dose of chemical exposures might affect DNA methylation patterns with implication for persistence of these effects across generations. The developmental exposures to EDCs such as BPA and DEHP may exert adverse effects on epididymal development.