Sheep thyroid gland cells isolated by a continuous- flow, trypsinization procedure were cultured as monolayers. The utilization of 13lI-iodide by such cultures was studied from 1 to 7 days in the presence and absence of TSH. 2. The 13lI uptake and its incorporation into each iodoamino acid (MIT, DIT and T4) decreased after the first day in culture. Addition of TSH at the start of culturing consistently enhanced the 13lI uptake and its incorporation into iodoamino acids from the 3rd to 7th days of culture. By the 7th day, the 13lI recovered as MIT, DIT and T4 in the cells of TSHtreated cultures was 260, 660 and 520%, respectively, of the control values. 3. Only MIT and DIT were present in the protein-bound 13lI of the medium. The amounts of these iodoamino acids did not increase with time in either control or TSH-treated cultures. 4. 13lI-T4 was recovered in the free form from the incubation medium, and its amount increased with time in the TSH-treated cultures. 5. Fractionation of cells from 3-day cultures revealed that 40-60% of the 13lI was in the soluble fraction. Addition of TSH to the cultures increased the 13lI content of this fraction by 330%. Of the 13lI recovered as iodoamino acids in the cells, 40 and 70% were found in the soluble fraction of control and TSHtreated cells, respectively. (Endocrinology75: 537,1964)
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Kerkof et al. (1964) studied this question.