The previous report from our institute has shown that the long-term treatment of cockerel with iodide indueed a goiter as well as a decrease in thyroxine-
131I and
131MIT/
131DIT ratio.
In order to elucidate the metabolism of stable iodine in the goitrous cockerels, the following experiments were made.
For this purpose, column chromatography using DOWEX, 1× 2, Cl
-form, 200-400 mesh was employed. This resin is able to absorb large doses of inorganic iodine and this column chromatography is more excellent in recovery of thyronine fraction and is more convenient in chemical analysis of stable iodine than paper chromatography.
The plasma thyronine level was also assayed by using this mathod.
1) After treatment of cockerels with iodine (1 mg/day) for 4 weeks, tracer
131I was injected and thyroids were removed 24 hours later Thyroid hydrolysate was fractionated by column chromatography and both
131I and
127I in the fraction were determined. Distribution of
127I was compatible with that of
131I, thyronine proportion decreased (0.01<p< 0.05) and MIT/DIT ratio was low. (p<0.001).
2) After treatment with a diet containing both
131I and
127I, decrease in MIT/DIT ratio (0.01<p<0.05) and thyronine proportion (p<0.001) were demonstrated.
Specific activity of
131I in the gland was identical with that in the diet after equilibrium study for 5 weeks.
3) In goitrous cockerels treated with iodine, total
131I content increased to 7 times and thyronine
127I to 3 times as much as controls. One week after discontinuance of a 4-week-iodine treatment, total
131I content dereased depending on the decrease of DIT.
4) In iodide-treated cockerels, plasma thyronine-
127I, half-life of
131I-labeled thyronine and daily degradation of thyronine were not different from controls.
Decrease rate of thyronine synthesis (especially coupling process) and of hormone release as possible causes for the goiter in the iodide-treated cockerels were discussed.
