THE EFFECT OF MANGANESE DEFICIENCY ON PAR AMETERS OF THYROID-HORMONE METABOLISM IN RATS

The effect of manganese deficiency on parameters of thyroid-hormone me tabolism in rats The effect of manganese deficiency on parameters of t hyroid-hormone metabolism was examined in two experiments with 24 male , weanling, Sprague Dawley rats per experiment. The animals were fed a semisynthetic casein-based diet containing either 0.2 mg Mn/kg (manga nese deficient diet) or 40 mg Mn/kg (control diet). The activity of ar ginase in liver was chosen as the criterion for determining the mangan ese status of the rats, and was clearly lowered in both experiments by manganese deficiency. While being unchanged in experiment 1, the live weight of the manganese-deficient animals at the end of experiment 2 was significantly reduced in contrast to control. The concentration of T-3 in the serum of the deficient animals was decreased in experiment 1, while tending to be increased in experiment 2. The concentration o f T-4 in the serum of the manganese-deficient rats was significantly d ecreased in both experiments (experiment 1: -18 %; experiment 2: -31 % ). The concentration of free T-4 in serum was not changed by manganese deficiency. The activity of hepatic deiodinase was increased in both experiments in manganese-deficient rats (experiment 1: 35 %, ns; exper iment 2: 48 %). The results of this investigation show a potential rol e for manganese in thyroid-hormone metabolism.