Effects of Endocrine Disrupting Chemicals on Monoamine Neurotransmitter

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13833007
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Institution: Osaka City University
• Principal Investigator: HIROI Toyoko Osaka City University, Medical School, Lecturer, 大学院・医学研究科, 講師 (30305643)
• Project Period (FY): 2001 – 2002
• Keywords: Endocrine Disrupting Chemicals / Bisphenol A (BPA) / Dopamine / Central Nervous Systems / Protein Disulfide Isomerase (PDI) / Thyroid Hormone / Bisphenol A-Binding Protein

Research Abstract

We searched for the Bisphenol A (BPA) binding protein in the rat brain. The membrane fractions (P2) prepared from rat brains had relative high BPA binding activity. The BPA-binding activity in P2 membrane fractions was not inhibited by estradiol, indicating that the BPA-binding proteins in this fraction was not estrogen receptors. We tried to purify the BPA-binding proteins from rat P2 fractions, monitoring BPA-binding activity using [3H]-BPA. The membrane proteins in P2 fractions were solubilized by sucrose monolaurate. After Whatman DE52 ion-exchange chromatography, the samples were applied on BPA-affinity chromatography. We designed BPA derivatives having useful groups for coupling with sepharose resin. Finally a single protein band was identified in the eluted fractions from BPA-affinity chromatography. The N-terminal amino acids were identical with that of Protein Disulflde Isomerase (PDI). Recombinant Protein Disulfide Isomerase (rPDI) was expressed in E. coli. The rPDI has BPA-binding activity and its kinetic parameter was similar to that of rat brain P2 fractions. These results means the BPA-binding protein in rat P2 membrane fractions is PDI proteins. The binding activity of PDI to BPA has not been reported until now. Furthermore BPA inhibited the binding of thyroid hormone to PDI. This result suggested that the binding of BPA to PDI might influence thyroid hormone dynamics, which is known to be very important for the development of central nervous systems in prenatal and lactational periods.
We also developed the in vitro detection assay for neural effects of BPA. The short-term exposure of BPA on PC 12 cells dose-dependently induced dopamine release from the cells. This assay might be useful for the investigation and screening for endocrine disrupting chemicals having neural effects like BPA.