title: 1,25-Dihydroxycholecalciferol modulates 3H-thymidine incorporation in FRTL5 cells.
abstract: 1,25-dihydroxycholecalciferol (1,25(OH)2D3) possesses proliferation and differentiation modulating effects in many cell types in vitro. We studied the effect of 1,25(OH)2D3 on 3H-thymidine incorporation in FRTL5 cells, a cultured rat thyroid follicular cell line. 1,25(OH)2D3 alone at 10(-11) and 10(-9) M exerted no effect on 3H-thymidine incorporation. However, at 10(-7) M, 1,25(OH)2D3 slightly enhanced 3H-thymidine incorporation. In the presence of 5% calf serum, 1,25(OH)2D3 increased 3H-thymidine incorporation induced by calf serum in a dose-dependent manner. 1,25(OH)2D3 also enhanced 3H-thymidine incorporation induced by PMA, an extrinsic stimulator of protein kinase C, without directly affecting PMA-induced protein kinase C translocation. In contrast to the stimulatory effects of 1,25(OH)2D3 on the calf serum and PMA-induced 3H-thymidine incorporation, 1,25(OH)2D3 inhibited the increase in 3H-thymidine incorporation induced by TSH in a dose-dependent manner. This effect of 1,25(OH)2D3 on TSH-induced 3H-thymidine incorporation may be, in part, due to post-cAMP pathways since 1,25(OH)2D3 also inhibited the increase in 3H-thymidine incorporation induced by Bu2cAMP without affecting the TSH-induced increase in cAMP. The stimulatory effect of insulin on 3H-thymidine incorporation, a cAMP-independent process, was also inhibited by 1,25(OH)2D3. We conclude that 1,25(OH)2D3 affects 3H-thymidine incorporation in FRTL5 cells raising the possibility of a physiologic role for 1,25(OH)2D3 in the growth and function of thyroid follicular cells.
authors.affiliation: Division of Endocrinology and Metabolism, University of Massachusetts Medical School, Worcester 01655.
authors.forename: B
authors.initials: B
authors.lastname: Ongphiphadhanakul
authors.forename: S A
authors.initials: SA
authors.lastname: Ebner
authors.forename: S L
authors.initials: SL
authors.lastname: Fang
authors.forename: A
authors.initials: A
authors.lastname: Lombardi
authors.forename: D T
authors.initials: DT
authors.lastname: Baran
authors.forename: L E
authors.initials: LE
authors.lastname: Braverman
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000502:physiology*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism*; D013961:Thyroid Gland / Q000378:metabolism*
chemical_list: D000242:Cyclic AMP; D011493:Protein Kinase C; D002117:Calcitriol; D013755:Tetradecanoylphorbol Acetate; D013936:Thymidine