C. L. Gaworski, Catherine Aranyi, Stanley C. Vana
1991
Citations
0
Influential Citations
3
Citations
Journal
Toxicological Sciences
Abstract
Abstract 2-Mercaptobenzimidazole (2-MBI), used in rubber prucessing, is a suspect carcinogen structurally related to ethylene thiourea. The inhalation toxicity of 2-MBI was evaluated in male and female F344 N rats exposed 6 hr/day, 5 days/week to respirable aerosols generated by spray atomization of aqueous suspensions of the 2-MBI powder and subsequent drying of the resulting aerosols. Twelve exposures at target concentrations of 0, 6.3, 12.5, 25.0, 50.0, or 100 mg/m3 of 2-MBI produced a dose-related reduction in body weight gains, thyroid follicular cell hyperplasia, adrenal cortex fatty change, and pituitary atrophy. Subchronic exposures were conducted at target concentrations of 0, 3.1, 6.2, 12.5, 25.0, and 50.0 mg/m3 of 2-MBI. Rats at ≥25 mg/m3 displayed hunched posture, hypoactivity, and reduced body weight gain, with compound related mortality at the highest exposure level. Anemia; increased SGPT, SGOT, alkaline phosphatase, sorbitol dehydrogenase, BUN, and cholesterol; and reduced free fatty acid were seen in rats at ≥25 mg/m3. Increased thyroid weight and thyroid follicular cell hyperplasia were noted in both sexes at ≥6.2 mg/m3, with reduced triiodothyronine and thyroxine levels in both sexes at ≥12.5 mg/m3. Thyroid follicular cell hyperplasia was also seen in rats at 3.1 mg/m3. Thymus weights were significantly reduced in both sexes at all exposure levels with liver weight increases at ≥6.2 mg/m3. Exposure-related histopathologic changes included pituitary cytoplasmic vacuolization, adrenal cortex necrosis, lymphoid depletion, thymic atrophy, liver cell hypertrophy, renal mineralization and tubular atrophy, and hypocellularity of the bone marrow.