Experimental studies of the di-n-butyl phthalate and mono-(2-ethylhexyl) phthalate effect on testicular development in rodents

Abstract

The postnatal development of the testes involves proliferation and differentiation of three cell types: Sertoli cells, Leydig cells and adult stem cells. The gonocytes are the precursors of male germ cells found in the fetal and neonatal period. The neonatal differentiation is critical to reproductive function and involves resumption of proliferative activity, drive to the base of the seminiferous epithelium and differentiation into spermatogonia. Studies have revealed that these cells are direct targets of endogenous androgens and endocrine disruptors that act as anti-androgens. The di-n-butyl phthalate (DBP) is an example of an endocrine disrupter which can cause inappropriate initiation of cell division and an increase in the number of Leydig cells due to a decrease in testosterone levels in the fetal testis. Although in the fetal period the proliferative activity of gonocytes is androgen-dependent, there is evidence that androgen sensitivity is lost in the transition to spermatogonia. There is also evidence of antiandrogenic action of DBP in the testis of other rodents, but it remains unknown to the Mongolian gerbil. This study aims to evaluate whether gestational exposure to di-n-butyl phthalate interferes with the postnatal development of the testis of the Mongolian gerbil, particularly in gonocytes. We will use male offspring of mothers treated with DBP and non-treated mothers at ages 1, 7, 14, 28 and 35 days postpartum (n = 12 per group). The DBP will be administered by gavage at a concentration of 100 mg/kg/day in the gestational days 8-24. The testes will be processed for light microscopy and, based on morphometric and stereological methods, it will be assessed the total number of gonocytes of neonates and the volume of major tissue components of this organ. It will also be examined the kinetics of proliferation and death of gonocytes, based on immunocytochemical tests for proliferating cell nuclear antigen (PCNA), the protein VASA and the TUNEL method. It will be analyzed the variations of sex steroids in plasma levels and testicular expression of androgen receptor (AR), estrogen receptor ± (ER±) and the enzyme 17² - hydroxysteroid dehydrogenase (17² - HSD). This proposal will expand the knowledge on the mechanisms related to the differentiation of neonatal gonocytes in situations of steroid change in intrauterine environment as a result of exposure to phthalate. (AU)