Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Iodine Deficiency Mitigates Growth Retardation and Osteopenia in Selenium-Deficient Rats

Animals and diets. Female Wistar rats (12 wk old; Iffa Credo) were housed in a light- and temperature-controlled room and fed a seleniumdeficient and iodine-adequate diet (Se2/I1), a selenium-adequate and iodine-deficient diet (Se1/I2), or a selenium-deficient and iodine-deficient diet (Se2/I2) for a minimum of 42 d before being mated with selenium-adequate male rats. The selenium-deficient diet, the same as that used in previous studies (6,13), contained 0.005 mg selenium/kg and used torula yeast as a protein source. The iodinedeficient diet contained 0.05 mg iodine/kg. The selenium-adequate diet contained 0.19 mg selenium/kg (Hope Farms). The diet composition is presented in Table 1. During pregnancy, female rats were housed in individual plastic cages. After delivery, the pups were kept with their dams and fed the same diet. At d 21, male offspring were housed separately and continued to be fed the same diet until the end of the experiment at d 74. A set of control male (Se1/I1) rats was obtained by mating female and male rats fed the same seleniumdeficient diet supplemented with 0.19 mg of selenium/kg. From weaning until the end of the experiment, individual pair-feeding was performed every day. A pair-fed control rat was fed a seleniumadequate diet in the same amount as that consumed the day before by its selenium-deficient counterpart, taking food spillage into account.

            Starting on d 21, tail length and body weight of 2nd-generation weanling male rats were measured 1 time/wk until the end of the experiment. Rats were placed in metabolic cages on d 73 for a 24-h urine collection to measure deoxypyridinoline, calcium, and phosphate. On d 74, rats were anesthetized with ether; blood was drawn by cardiac puncture using a heparinized syringe, and the rats were then killed humanely by decapitation. Femurs and tibias were removed and cleaned, and pituitaries were dissected and frozen.

            Assays. Erythrocyte glutathione peroxidase activity (Gpx) was measured spectrophotometrically at 340 nm, after elimination of leukocytes and platelets, by the decrease in NADPH (0.2 mmol/L) using glutathione (1 mmol/L) and H2O2 (0.15 mmol/L) as substrates (15,16). The enzyme unit of Gpx was defined as 1 nmol of reduced NADPHoxidized perminute. Plasma and urinary calciumand phosphate were determined by colorimetry using o-cresolphthalein and phosphomolybdate, respectively (Hitachi Modular-P, Roche Diagnostic). Plasma proteins were determined by the Biuret method. Commercial RIA kits were used to measure plasma thyroxine (T4), triiodothyronine (T3) (Amersham), and insulin-like growth factor (IGF-I; Biosource). Osteocalcin was measured using a rat-specific RIA kit (Biomedical Technologies). Urinary deoxypyridinoline was measured by an automated immunoassay with chemiluminescence detection (Immulite, Diagnostic Products) and commercial reagents (Diagnostic Products). The individual pituitaries were homogenized in 150 mL distilled water and frozen. They were later thawed and diluted 20-fold in phosphosaline buffer, pH 7.4, containing 1% bovine serum albumin.

untuk melihat naskah Aslinyaa >> download here !!