[In vitro study of deiodination of L-diiodotyrosine and L-thyroxine in liver of dietetically fat rats].

Beginning with the fifth week of life, male Wistar rats were fed a diet containing, respectively, 3 and 50 per cent fat (corresponding to, respectively, 7 and 75 per cent fat of total calories). The differences in body weight between the two groups were 64 per cent for 10-week-old rats, and 71 per cent for 6-month-old rats. For these animals, the extent of the enzymatic deiodination of L-diiodotyrosine and L-thyroxin was determined in liver homogenate supernatants. In the 10-week-old rats as well as in the 6-month-old rats on high-fat diet, the deiodination of L-di-iodotyrosine was significantly lower than in the animals on low-fat diet, whereas the diodination of L-thyroxin was significantly higher. It is concluded that the fat content of the diet exerts an inhibiting effect on the deiodination of L-di-iodotyrosine and an enhancing effect on the deiodination of L-thyroxin.