EFFECT OF SODIUM SELENITE ON GROWTH, INSULIN-LIKE GROWTH FACTOR-BINDING PROTEINS AND INSULIN-LIKE GROWTH-FACTOR-I IN RATS

Selenium is an essential trace element although at higher doses iris also known to be a toxic agent causing a wide range of symptoms including growth retardation. In order to investigate the effect of sodium selenite on growth, insulin-like growth factor-binding proteins (IGFBPs) and insulin-like growth factor-I (IGF-I), 30 male Wistar rats were randomized into three groups. Group A was treated with sodium selenite in the drinking water (3.3 mg selenium/I). Group B was an libitum fed with free access to standard fodder and tap water and group C was pair fed relative to the selenium-treated rats. Serum IGF-I and IGFBPs were determined on days 0, 14 and at the end of the study on day 35. Selenium-treated rats had significantly lower body weights compared with group B rats on day 9 and group C rats on day 14 (P<0.05). Tibia length was measured at the end of the study and no difference was observed between groups B and C (3.77+/-0.04 cm vs 3.60+/-0.02 cm); however, selenium-treated rats had significantly shorter tibia lengths (3.46+/-0.03 cm) compared with rats in groups B (P<0.001) and C (P<0.05). Selenium treatment induced a significant reduction in circulating IGF-I by the end of the study compared with ad libitum and pair fed rats (P<0.05). Serum subjected to Western ligand blots showed four distinct IGFBP bands with apparent relative molecular weights of 38-47 kDa (doublet) (IGFBP-5), 30 kDa (IGFBP-1 and/or IGFBP-2) and 24 kDa (IGFBP-4). At the end of the study a significant reduction in IGFBP-5 was observed in group A compared with groups B and C (P<0.05). Selenium treatment also caused a reduction in IGFBP-1 and/or IGFBP-2 compared with an libitum fed rats; in addition, a reduction was observed in pair fed controls. In conclusion, sodium selenite treatment leads to growth retardation accompanied by reduced circulating levels of IGF-I, IGFBP-3, and IGFBP-1 and/or IGFBP-2. The reduction in IGF-I and IGFBP-5 could not be attributed to reduced caloric intake but seems to be a specific action of selenium.