title: Regulatory effect of 1,25-dihydroxycholecalciferol on calcium fluxes in thyroid FRTL-5 cells.
abstract: The aim of the present study was to investigate the effect of 1,25-dihydroxycholecalciferol (1,25(OH)2-D3) on the regulation of calcium fluxes in rat thyroid FRTL-5 cells. The ATP-induced uptake of 45Ca2+ was decreased in cells pretreated with 1,25(OH)2D3 for 48 h. No effect was seen on basal uptake of 45Ca2+. At least a 24 h incubation period was required for the effect of 1,25(OH)2D3 to be expressed. Pretreatment with 1,25(OH)2D3 for 48 h did not change resting intracellular Ca2+ ([Ca2+]i) in fura-2-loaded FRTL-5 cells. However, the ATP-induced increase in [Ca2+]i was significantly enhanced in cells preincubated with 1,25(OH)2D3. The effect of 1,25(OH)2D3 was abolished in Ca(2+)-free buffer. No difference in the ionomycin-induced increase in [Ca2+]i was observed between control cells and cells pretreated with 1,25(OH)2D3. However, in Ca(2+)-free buffer the ionomycin response was decreased in cells incubated with 1,25(OH)2D3. The ATP-induced change in [Ca2+]i was decreased when ATP was added after ionomycin to cells treated with 1,25(OH)2D3. The results suggest that 1,25(OH)2D3 has a regulatory effect on Ca2+ fluxes in FRTL-5 cells, possibly by acting on Ca2+ sequestration.
authors.affiliation: Endocrine Research Laboratory, University of Helsinki, Finland.
authors.forename: K
authors.initials: K
authors.lastname: Törnquist
authors.forename: P
authors.initials: P
authors.lastname: Stewen
authors.forename: C
authors.initials: C
authors.lastname: Lamberg-Allardt
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002478:Cells, Cultured; D015759:Ionomycin / Q000494:pharmacology; D051381:Rats; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013268:Stimulation, Chemical; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D015759:Ionomycin; D000255:Adenosine Triphosphate; D002117:Calcitriol; D002118:Calcium