Goitrogenic Action of Manganese on Female Mouse Thyroid through Three Generations : Endocrinology

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The effect of manganese on mouse thyroids was examined through three generations. The continuous supply of drinking water containing 200mg/l MnCl_2-4H_2O induced mild goiter only in female mice. The manganese treatment did not significantly affect the serum thyroxine (T_4) levels in dams or the plasma levels in neonates, suggesting that the effect was not severe. The syntheses of T_4 and triiodothyronine (T_3) were examined in hydrolyzed thyroids. The results showed that ratios of radioiodide activity in hormonal fractions of the manganese-given groups to those of control groups were greater than 1 for all three generations of female mice. These results indicated that newly synthesized hormones were retained in thyroids of the manganese-treated female mice. On the other hand, in males, the ratio was reduced to less than 1 as the numbers of generations increased. "Dwarf" neonates born in the third generation of the manganese-treated group showed an ataxial motion in their gait of walk. However, histological examination of cerebral and cerebellar regions of the dwarfs revealed no severe changes.
1988-10-15