K. Eder et al., THE EFFECT OF MANGANESE SUPPLY ON THYROID-HORMONE METABOLISM IN THE OFFSPRING OF MANGANESE-DEPLETED DAMS, Biological trace element research, 55(1-2), 1996, pp. 137-145
The present study was performed to investigate the effect of manganese
(Mn) supply on metabolism of thyroid hormones in the rat. A study wit
h rats was carried out over two generations. Female rats were raised w
ith a Mn-deficient diet (0.1 mg Mn/kg), and mated to produce a second
generation. The male rats of the second generation were used as subjec
ts for the investigation They were divided into five groups and fed di
ets with Mn concentrations of 0.1, 0.5, 2.2, 10, and 46 mg/kg for 40 d
. For assessment of thyroid hormone metabolism, concentrations of thyr
oid hormones in serum and activity of hepatic type I 5'deiodinase (5'D
-I) were measured. Feeding diets with 0.1 mg Mn/kg impaired growth and
food conversion, influenced parameters of thyroid hormone metabolism,
and changed some clinical-chemical parameters, such as concentrations
of total protein, albumin, calcium (Ca) and magnesium (Mg) as well as
activity of alkaline phosphatase in serum. Regarding the thyroid horm
one metabolism, rats fed the diet with a Mn level of 0.1 mg/kg had a h
igher 5'D-I activity in liver, and consequently a higher concentration
of triiodothyronine in serum than the rats fed the other diets. Ln co
ntrast, the concentrations of total and free thyroxine were not influe
nced by the Mn intake. Growth, clinical-chemical parameters, concentra
tions of thyroid hormones in serum, and activity of hepatic 5'D-I were
similar in the rats fed diets with Mn concentrations between 0.5 and
46 mg/kg. The present study shows that feeding a diet with a very low
Mn concentration affects growth and thyroid hormone metabolism and tha
t a dietary level of 0.5 mg Mn/kg is adequate for growth and thyroid h
ormone metabolism in the offspring of Mn-depleted dams.