The Endocrine Disrupters Butyl Benzyl Phthalate and Bisphenol A Increase the Expression of Progesterone Receptor Messenger Ribonucleic Acid in the Preoptic Area of Adult Ovariectomized Rats

Abstract

Butyl benzyl phthalate (BBP) and bisphenol A (BPA), so-called endocrine disrupters, are known to mimic the action of estrogens: they are thus liable to influence reproductive functions. Since little is known about their action on gene expression in the adult hypothalamus, we examined the effects of these chemicals on the expression of estrogen-regulated mRNAs, i.e., progesterone receptor (PR) mRNA, preproenkephalin (PPE) mRNA and neurotensin (NT) mRNA, in the hypothalamus and pituitary of adult female rats. Two weeks after ovariectomy, rats were subcutaneously injected with 10 mg BBP, 10 mg BPA, or 10 µg 17β-estradiol (E₂) in sesame oil, or with sesame oil alone as a control. Twenty-four hours after the injection, tissues including the preoptic area (POA), mediobasal hypothalamus (MBH) and anterior pituitary were collected. Northern blot revealed that injection of E₂ resulted in expected changes, i.e., significant increases in PR mRNA in the POA, MBH and anterior pituitary, and in PPE mRNA in the MBH. We also found that injection of BPA significantly increased PR mRNA in the POA and anterior pituitary, while injection of BBP increased PR mRNA in the POA and anterior pituitary, although the increase in the anterior pituitary was not significant. No significant effect of E₂, BPA, or BBP on NT mRNA in the POA was detected. The present study demonstrates that the two endocrine disrupters BPA and BBP can increase the expression of PR mRNA in the POA of adult ovariectomized rats.