RP8 Ecotoxicology of Agrochemicals and Pharmaceuticals
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(MOR-1117-608178) Effects of exposure to pentachlorophenol during gestation and lactation on neuro-endocrine system in rats.

Morohoshi, K^{1, 2}, Kawaguchi, M³, Takano, H^{1, 2}, Morita, M¹, Yamamoto, H⁴, Kondo, T¹, Himi, T³, Imai, H^{1, 2}, ¹ National Institute for Environmental Studies, Tsukuba, Japan² The Master’s Program in Environmental Sciences, University of Tsukuba, Tsukuba, Japan³ Department of Toxicology and Pharmacology, Faculty of Pharmacy, Musashino University, Musashino, Japan⁴ Faculty of Integrated Arts and Studies, University of Tokusima, Tokushima, Japan

ABSTRACT- Thyroid hormone (TH) is essential for the developing central nervous system. Recently, epidemiological and experimental studies have shown that endocrine disrupting chemicals (EDCs) disturb TH systems. On the other hand, hypothyroidism in pregnant mother causes delay of child's mental development and the following low IQ. Pentachlorophenol (PCP) is one of EDCs which affect TH systems. In this study, we examined whether gestational and lactational exposure of PCP to pups affect the neuroendocrine system and the stress responses. PCP was administered to mother rats (Wistar) via drinking water (6.6 mg/L) ad libitum from gestational day 0 to postnatal day 21. Control group was given distilled water. Furthermore, a part of twelve-week-old pups was exposed to immobilization stress for five days (three hours /day). Liver, blood and brain samples were collected from three-day-old, three-week-old and twelve-week-old pups, and mothers after weaning. Blood samples were not collected from three-day-old pups. PCP concentrations in liver, plasma and brain were determined using GC-MS. Plasma levels of TH and corticosterone were determined by radioimmunoassay. Stress-induced neuronal cell death in hippocampus was estimated by counting apoptotic cells using TUNEL (Terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling) method. Thyroxine concentrations in plasma of PCP-treated mothers and PCP-treated pups (three-week-old) were significantly lower than those of control mothers or control pups, respectively. Significant difference of thyroxine concentration in plasma was disappeared between PCP-treated pups (twelve-week-old) and control pups (twelve-week-old). Stress-induced corticosterone levels in plasma and the number of TUNEL-positive cells in hippocampus of PCP-treated group were not significantly different from those of control for twelve-week-old pups. PCP exposure transiently affected for TH systems, however, stress responses was not affected by PCP exposure.

Key words: Pentachlorophenol, Thyroid hormone, Stress, Rat