Effects of goitrin on in vitro hormone biosynthesis by the chick thyroid

The effect of graded doses of goitrogen such as goitrin, PTU, AITC and KCIO4, on the in vitro biosynthesis of thyroid hormone was studied in chicks. Thyroid lobes dissected from the chick fed goitrogen or without dietary goitrogen were incubated in 3 ml KRP buffer, pH 7.4 at 370C with 20 μ Ci carrier-free 131I. Thyroidal 131I uptake was depressed by 10-5 M of KClO4 but not significantly depressed by 10-6 to 10-4 M of goitrin, PTU and AITC. Thyroidal 131I uptake in vitro by the thyroid lobes of chicks fed goitrin or PTU was accelerated in comparison with that without goitrogen. Ratios of MIT/DIT were elevated and iodothyronine synthesis was depressed in proportion to concentration (10-7 - 104 M) of goitrogen added. Monoiodination of tyrosine in the thyroid was depressed at the level of 10-5 M of KClO4 and 10-4 M of goitrin or PTU. In vitro iodothyronine biosynthesis was depressed by 10-6 M of goitrin or PTU in the thyroid of chicks fed with or without goitrin or PTU. (auth.)