10D0PR0TEINS IN NORMAL AND ABNORMAL HUMAN THYROID TISSUE AND IN NORMAL SHEEP THYROID1

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Abstract
Two types of iodoproteins other than thyroglobulin have been found in normal and abnormal human thyroid tissue and in normal sheep thyroid. They are similar to, but not identical with, iodoproteins previously described in a functioning rat thyroid tumor, and were detected in tissue labeled with I131 either in . vivo or in vitro. One of these iodoproteins, termed "particulate iodoprotein" or "P-1" was not extractable from thyroid homogenates with 0.15 M NaCl. It comprised from 1 to 6% of the organic radio-iodine in normal thyroids and in several abnormal thyroid tissues, but was 37% in a follicularcarcinoma. The second iodoprotein, termed "S-1 iodoprotein," was soluble in 0.15 M NaCl, but differed from thyroglobulin in other physical properties. It was more soluble than thyroglobulin in phosphate buffer, sedimented more slowly in the ultracentrifuge, and had a faster electrophoretic mobility. It comprised from 1 to 7% of the extractable organic radioiodine in normal and in a wide variety of abnormal thyroids, but was as high as 19% in a follicular thyroid adenoma. Thyroid S-l iodoprotein resembles iodoprotein previously described in the blood of abnormal human subjects. One poorly differentiated thyroid carcinoma, which had been labeled in vitro, contained iodoprotein which differed from that found in the other tissues. Thyroglobulin in human and sheep thyroid tissue differed slightly from rat thyroglobulin in solubility in phosphate buffer and in electrophoretic mobility. There was also a small difference in electrophoretic mobility detected between thyroglobulins in the various human tissues. The manner in which the non-thyroglobulin iodoproteins participate in thyroid physiology is not yet understood.