IODOTHYRONINE DEIODINASE ACTIVITY IN METHIONINE-DEFICIENT RATS FED SELENIUM-DEFICIENT OR SELENIUM-SUFFICIENT DIETS

We examined the effect of methionine deficiency on iodothyronine 5'-de iodinase activity in selenium-deficient rats or selenium-sufficient ra ts fed sodium selenate or selenomethionine. Forty-two weanling male Wi star rats were divided into six groups and pair fed the respective pur ified L-amino acid-based diets for 4 wk. L-methionine concentrations i n the-diet were 8.0 g/kg for sufficient rats, and 2.0 g/kg for deficie nt rats. Selenium concentrations in the diet were 0.5 mg/kg (as sodium selenate or selenomethionine) for selenium-sufficient rats and less t han 0.005 mg/kg for selenium-deficient rats. Type I 5'-deiodinase acti vities were significantly lower in liver and higher in kidney of methi onine-deficient rats than in those of methionine-sufficient rats fed e ither the selenium-sufficient or the selenium-deficient diets. The typ e I 5'-deiodinase activity in brain was significantly lower in the met hionine-deficient rats than in the methionine-sufficient rats fed the selenium-deficient diet. Type II 5'-deiodinase activity in brain was s ignificantly higher in the methionine-deficient rats than in the methi onine-sufficient rats fed selenium-sufficient diet as sodium selenate. Both thyroxine and 3,3',5-triiodothyronine concentrations in plasma w ere significantly higher in the methionine-deficient rats than in the methionine-sufficient rats. It is suggested that the methionine defici ency affects the 5'-deiodinase activity and thyroid hormones level in the rats.