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Effects of Thyrotropin on Iodine Metabolism of Dog Thyroid Cells in Tissue Culture^*

PAUL A. WADELEUX, JACQUELINE ETIENNE-DECERF, ROGER J. WINAND and LEONARD D. KOHN

The Département de Clinique et de Sémiologie Médicates, Institut de Médecine, Université de Liège B-4020 Liège, Belgium (PA. W., J.E.D., and R.J.W.)
The Section on Biochemistry of Cell Regulation, Laboratory of Biochemical Pharmacology, National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health Bethesda, Maryland 20014 (L.D.K.)

Abstract

When grown in the presence of thyrotropin, dog thyroid cells in culture form follicle-like structures, take up labeled iodide, and iodinate macromolecular components in the cell. When grown in the absence of thyrotropin, dog thyroid cells in culture form a monolayer, take up only 6% of the iodide of follicular cells, and do not iodinate macromolelcular components in the cell. The iodide uptake in monolayer cells does, however, reflect an incorporation process unique to thyroid cells because hepatocytes and fibroblasts do not have the capacity of the monolayer cells to take up iodide. Thyrotropin stimulation of monolayer cells for a prolonged period (3–8 days) causes the cAMP levels of these cells to return to levels identical to those in follicular cells. The increased cAMP levels are not due to the induction of an adenylate cyclase enzyme, because homogenates of monolayer cells have a thyrotropinstimulable adenylate cyclase activity. The low level of cAMP, thus, seems to be a problem of receptor coupling to the adenylate cyclase enzyme. The return of cAMP to normal levels is accompanied by an increase in iodide uptake and by macromolecular organification; the return of cAMP levels to normal values is not accompanied by follicular development. The majority (75%) of the iodinated macromolecular product accumulated by follicular thyroid cells, by monolayer thyroid cells stimulated with thyrotropin for a prolonged period, or by thyroid cells treated with dibutyryl cAMP from the onset of culture has the characteristics of 19 S thyroglobulin. The remainder appears to be low mol wt material which may be thyroglobulinrelated i.e., be either precursor or biodegraded material. (Endocrinology 102: 889, 1978)

Footnotes

^* Portions of this work were presented in preliminary form both at the 94^e Réunion de le Société Beige de Biochimie, Louvain, Belguim, October 18, 1975, and at the Workshop Conference on the Biochemical Basis of Thyroid Stimulation and Thyroid Hormone Action, Celle, Germany, September 26–27, 1975.

To whom requests for reprints should be addressed.

Received June 13, 1977.