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Neuroimmunological effects of exposure to methylmercury forms in the Sprague-Dawley rats. Activation of the hypothalamic-pituitary-adrenal axis and lymphocyte responsiveness.

Abstract：

:The effects of different methylmercury (MeHg) forms on the immune system and the hypothalamic pituitary adrenal (HPA) axis were assessed. The lymphocyte response to Concanavalin A (Con A) stimulation, blood levels of interleukin-6 (IL-6), adrenocorticotrophin hormone (ACTH), and corticosterone in the presence of different MeHg compounds was measured. Rats were exposed to methylmercury sulfide [(MeHg)2S] and methylmercury chloride (MeHgCl) at concentrations of 5 and 500 micrograms per liter in the drinking water for 8 or 16 weeks. Short-term exposure (8 weeks) at both, low- and high-doses of (MeHg)2S significantly enhanced lymphocyte responsiveness. MeHgCl only induced increased lymphocyte responsiveness at the low-dose exposure. Circulating levels of IL-6 after short-term exposure were increased in the MeHgCl-exposed group. The HPA axis activation was demonstrated by increased levels of ACTH and corticosterone levels. This response was predominant in low-dose exposed animals. Long-term (16 weeks) exposure resulted in a reduction in lymphocyte prolife ration after both low- and high-dose MeHgCl exposures. The (MeHg)2S exposure resulted in a 3-fold increase in the proliferative response. Levels of ACTH were elevated 3-fold in the (MeHg)2S-exposed group and no increase of corticosterone was observed in the high-dose exposed group at 8 weeks, no effect of (MeHg)2S was observed at 16 weeks. The MeHgCl exposed group showed an increase in ACTH and corticosterone levels at 8 weeks; this response was not observed at 16 weeks. These data indicate that exposure to MeHg compounds enhances T-cell proliferation in most of the cases, in a dose- and time-dependent fashion. Release of IL-6 also depends on the length of exposure. Early increases in circulating ACTH at 8 weeks also suggest activation of the HPA axis. This may contribute to the production of IL-6 and surveillance of regulatory homeostatic responses against environmental agents that mimic stress-like responses.

journal_name

Toxicol Ind Health

journal_title

Toxicology and industrial health

authors

Ortega HG,Lopez M,Takaki A,Huang QH,Arimura A,Salvaggio JE

doi

10.1177/074823379701300105

subject

Has Abstract

pub_date

1997-01-01 00:00:00

pages

57-66

issue

eissn

0748-2337

issn

1477-0393

journal_volume

pub_type

杂志文章

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Neuroimmunological effects of exposure to methylmercury forms in the Sprague-Dawley rats. Activation of the hypothalamic-pituitary-adrenal axis and lymphocyte responsiveness.