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Subchronic thyroid toxicity evaluation of 4,4'-methylenebis(N,N'-dimethyl)aniline in Fischer 344 rats

Darol E Dodd1, Linda J Pluta, Mark A Sochaski

  • 1The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina, USA.

Journal of Toxicology and Environmental Health. Part A
|June 21, 2012
PubMed

Insights

This study found that exposure to 4,4'-methylenebis(N,N'-dimethyl)aniline (MDA) in rats significantly impacted thyroid function and structure. The no-observed-adverse-effect level (NOAEL) for MDA was determined to be 200 ppm.

Area of Science:

  • Toxicology
  • Endocrinology
  • Animal Studies

Background:

  • 4,4'-methylenebis(N,N'-dimethyl)aniline (MDA) is an industrial chemical.
  • Thyroid hormones are crucial for metabolism and development.
  • Understanding chemical toxicity on the thyroid is vital for risk assessment.

Purpose of the Study:

  • To evaluate the toxicological effects of MDA on the rat thyroid gland.
  • To determine the dose-response relationship and identify a no-observed-adverse-effect level (NOAEL).

Main Methods:

  • Female F344 rats were fed diets containing MDA at various concentrations (0-750 ppm) for up to 13 weeks.
  • Evaluated endpoints included clinical signs, body weight, thyroid weight, serum thyroid hormones (TSH, T4, T3), and thyroid histopathology.
  • Statistical analyses were performed to assess MDA-related effects.

Main Results:

  • No MDA-related clinical signs of toxicity were observed.
  • Decreased body weight was noted at the highest MDA concentration (750 ppm).
  • MDA exposure led to increased TSH and decreased T4/T3 levels, along with thyroid weight increases and histopathological changes (follicular cell hypertrophy and hyperplasia) at concentrations ≥375 ppm.

Conclusions:

  • MDA exposure negatively affects thyroid hormone levels and thyroid gland structure in rats.
  • A NOAEL of 200 ppm was established for MDA, based on the absence of significant thyroid follicular cell hyperplasia at this dose.

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