Studies on rat thyroid after oral administration of mancozeb: morphological and biochemical evaluations.

Mancozeb, an ethylenebisdithiocarbamate (EBDC), has been studied for its effects on rat thyroid. Single oral administration of mancozeb at different concentrations (9600, 12,000, 15,000 and 18,750 mg kg(-1) body wt) has derived the oral LD50 value as 15,000 mg kg(-1) body wt. in male rats. Mancozeb at repeated oral doses of 500, 1000 and 1500 mg kg(-1) day(-1) for periods of 30, 90, 180 and 360 days has produced dose-dependent signs of toxicity and death of animals. The fungicide caused a significant increase in thyroid/body weight ratio and histopathological changes. Reduced levels of thyroid radioiodine ([125]I) uptake, serum protein-bound iodine (PB[125]I), thyroxine (T4) and reduced activity of thyroid peroxidase (TPO) have also been observed after exposure to mancozeb. Thus, mancozeb has been shown to produce marked structural and functional changes in thyroid of rats.