Journal of Cell Science, Vol 9, 49-69, Copyright © 1971 by Company of Biologists

Revised on October 26, 1970

The Preservation of Specialization by Dispersed Steer Thyroidal Cells in Long-Term Culture

¹ Department of Radiology, Stanford University School of Medicine Stanford, California 94305, U.S.A.; Departments of Radiology and Medicine, University of Missouri School of Medicine, Columbia, Missouri 65201, U.S.A.

Serially propagated cells derived from the steer thyroid gland preserve several specialized characteristics, some demonstrable for as long as 8 months (over 15 passes). For about 5 passes (3 months), follicular-like arrays of cells develop. Thyroid-stimulating hormone (TSH) or thyrotropin (1 and 10 mu./ml) induces the formation of supernumerary nucleoli, and promotes at the ultrastructural level the prompt (within 10 min) appearance of microvilli, pseudopodia, and intracytoplasmic droplets. These cells have a mean plating efficiency (PE) of 16.5 ± 4.5% (standard deviation) and with 3x10⁴ cells as the standard inoculum, a mean doubling time (T_d) of 43.7 ± 1.2 h. The linear variation of T_d with the number of cells seeded probably signifies strong cell-cell interactions. TSH (1-5o mu./ml) influences both PE and T_d, with 1 mu./ml producing the maximum stimulation. TSH (0.001-100 mu./ml) also induces the discharge of incorporated radio-iodide from the cultured thyroid cells, achieving a peak by 2-4 h, titres of 0.1-1 mu./ml being most potent. Long-acting thyroid stimulator (LATS) (0.2 u./ml) likewise effects release of ¹³¹I into growth medium (1 experiment), but over a more protracted period. After labelling with [³H]leucine, radioautographs demonstrate that the synthesis of proteins is stimulated by exposure to TSH (1 mu./ml). Precipitation with trichloroacetic acid indicates that these cells persist in synthesizing ¹³¹I-tagged iodoproteins, an activity optimally stimulated by 1 mu./ml TSH and marked by 3 h. Hence, such thyroidal cell lines afford a useful model for studying differentiation and hormonal effects.