Histological and immunohistochemical study on the adverseeffects of sodium chlorate on the pituitary–thyroid axis of albinorats and the possible protective effect of curcumin

BackgroundSodium chlorate (NaClO3) is found in drinking water, but it has a toxic effect onthyroid. However, curcumin has a thyroid-stimulating effect.Aim of the workTo study the effect of NaClO3 on the pituitary–thyroid axis of rats and determine thepossible protective role of curcumin.Materials and methodsThirty rats were divided into three groups of 10 rats each. Group I was the controlgroup. In group II, rats received 0.2 g/l of NaClO3 in drinking water for 3 weeks. Ingroup III, rats received curcumin (100 mg/kg) 1 week before exposure to NaClO3and it was continued for 3 weeks. T3, T4, thyroid-stimulating hormone, andsuperoxide anion were measured. Sections were subjected to H E, azan stain,caspase-3, and S-100 immunohistochemical stains.ResultsIn group II, serum T3 and T4 were significantly decreased whereas thyroid-stimulatinghormone and superoxide anion were significantly increased compared with thecontrol group. The thyroid gland showed follicular cell hypertrophy, hyperplasia,decreased colloid, and significantly decreased caspase-3 immunoreactivity comparedwith the control group. The pituitary gland showed significantly increased basophilsand significantly decreased S-100-positive folliculostellate cells compared withthe control group. In group III, thyroid function tests were significantly improvedcompared with group II, but did not reach the control level. Thyroid sections appearedapparently normal, with significantly increased caspase-3 immunoreactivity comparedwith the control group and group II. The pituitary gland showed basophils that weresimilar to those of the control group. S-100-positive folliculostellate cells weresignificantly increased compared with group II, but did not reach the control level.ConclusionCurcumin can protect the thyroid gland from the adverse effects of NaClO3 andconsequently protects the pituitary gland from negative feedback.