Rabbit Thyroid Metabolism in Tissue and Organ Culture. ∗

Abstract

Summary and conclusions

1. Organ cultured rabbit thyroid glands are able to concentrate I-131 from culture media and can incorporate the iodide into MIT, DIT, and T₄. 2. TSH accelerates all of these processes in organ cultured rabbit thyroid glands. 3. No evidence for the incorporation of C¹⁴ tyrosine or C¹⁴ phenylalanine into MIT, DIT, and T₄ could be found in histologically normal and apparently metabolically normal organ cultured thyroid glands. 4. The most probable explanation for this lack of incorporation of C¹⁴ phenylalanine and C¹⁴ tyrosine is that only a small proportion of tyrosine incorporation into thyroid protein is found as residues of thyroglobulin appropriate for iodination and generation into thyroid hormones. Thus the specific activity of the radioactive tyrosine in MIT, DIT, and T₄ would be too low to measure in spite of culturing in tyrosine-free media.