Follicular reorganization and 131-I utilization by cultured rat thyroid cells implanted into thyroidectomized rats

Rat thyroid gland cells were isolated by a trypsinization procedure and cultured for 3 days either in Gelfoam pads in a medium with no TSH or as monolayers in a medium containing 0.17 U of bovine TSH per ml. The cells cultured by the first method were implanted into rats 52-217 days after they had been thyroidectomized by surgical removal of the gland at 20-25 days of age followed by an 131I injection. The cells cultured by the second method were implanted into rats 19 and 20 days after they had been thyroidectomized by an 131I injection on the day of birth. In both cases the implanted cells reorganized into aggregations of follicles containing colloid in their lumens. Autoradiographs of sections of these reformed follicles revealed the presence of protein-bound 131I in the colloid. The implants in both groups of animals utilized radioiodine and formed labeled MIT, DIT, T4 and T3. Iodine metabolism of the implants in the second group of animals was similar to that observed in intact thyroid glands of norm...