Effect Of Selenium on Thyroid Biochemical and Histopathological Changes Induced by Subchronic Lead Acetate Exposure in Adult Albino Rats

We evaluated the effect of selenium on thyroid functions, oxidative stress and histopathological changes induced by subchronic lead acetate exposure. The study was for eight weeks on fifty adult albino rats of both sexes divided into five equal groups: negative control group (I), positive control group (II), positive control selenium group (III) in a dose of 0.35 mg/kg bw; orally per day daily, lead acetate group (IV) in a dose of 60 mg/kg bw; orally per day and selenium (0.35 mg/kg bw; orally per day) + lead acetate (60 mg/kg bw; orally per day) group (V). After eight weeks rats were anaesthetized by ether and blood samples were collected to evaluate thyroid functions in form of Triiodothyronine (T3), Total Thyroxin (T4) and Thyroid Stimulating Hormone (TSH) levels as well as blood lead level. Then animals were sacrificed and thyroid tissue was obtained and examined histopathologically and estimate lead content, malondialdehyde (MDA) and antioxidative enzyme superoxide dismutase (SOD).Results revealed significant decrease in both T3, T4 levels and increase in TSH and blood lead level in lead acetate group (IV) when compared with control group (I). An increase in lead content as well as malondialdehyde and decrease in superoxide dismutase in thyroid tissue was observed in lead acetate group (IV). Histopathologically, there was numerous variable sized thyroid acini lined by hypertrophied columnar epithelium and filled with homogenous eosinophilic colloid material showing peripheral scalloping.Rats treated with selenium + lead acetate group (V) showed increase in both T3, T4 levels and decrease in TSH and blood lead level but not returned to normal when compared with lead acetate group (IV). Additionally, decrease in lead content and malondialdehyde of thyroid tissue and increase in superoxide dismutase activity was observed when compared with lead acetate group (IV). Histopathologically, there were some acini filled with cubical epithelium with no peripheral scalloping.We concluded that selenium has an ameliorative effect on lead acetate induced biochemical and histopathological changes on thyroid gland.