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

Hector G. Ortega, Manuel Lopez, Atsushi Takaki, Qin Heng Huang, Akira Arimura, John E. Salvaggio

Research output: Contribution to journalArticle

10 Citations (Scopus)

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 μg 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 proliferation 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.

Original languageEnglish
Pages (from-to)57-66
Number of pages10
JournalToxicology and Industrial Health
Volume13
Issue number1
DOIs
Publication statusPublished - Jan 1 1997
Externally publishedYes

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Lymphocytes
Adrenocorticotropic Hormone
Sprague Dawley Rats
Rats
Corticosterone
Chemical activation
Hormones
Interleukin-6
T-cells
Immune system
Cell proliferation
Concanavalin A
Drinking Water
Immune System
Animals
Blood
Cell Proliferation
methylmercuric chloride
T-Lymphocytes

All Science Journal Classification (ASJC) codes

  • Toxicology
  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis

Cite this

Neuroimmunological effects of exposure to methylmercury forms in the Sprague-Dawley rats. Activation of the hypothalamic-pituitary-adrenal axis and lymphocyte responsiveness. / Ortega, Hector G.; Lopez, Manuel; Takaki, Atsushi; Huang, Qin Heng; Arimura, Akira; Salvaggio, John E.

In: Toxicology and Industrial Health, Vol. 13, No. 1, 01.01.1997, p. 57-66.

Research output: Contribution to journalArticle

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