title: Differential effects of 1,25-dihydroxyvitamin D3 on cytosolic calcium in two human cell lines (HL-60 and U-937).
abstract: 1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) has been shown to induce maturational changes in the human promyelocytic leukemia cell line HL-60 and in the human monocytic cell line U-937. Changes in cytosolic calcium have been reported to regulate cellular processes. We used the fluorescent dye Quin 2 to examine the effects of vitamin D metabolites on cytosolic calcium levels in HL-60 and U-937 cells. 1,25-(OH)2D3 (20 nM) increases cytosolic calcium by 24% over a 5-min period in HL-60 but not in U-937 cells. 1,25-(OH)2D3 (0.2 nM and 4 nM) has no effect on cytosolic calcium levels in either cell type. 24,25-(OH)2D3 (20 nM) has no effect on cytosolic calcium in HL-60 cells. Nifedipine (1 mM) has no effect on cytosolic calcium levels over 30 min and likewise does not block the 1,25-(OH)2D3-induced increase in cytosolic calcium in HL-60 cells. However, chelation of extracellular calcium with EGTA (10 mM) blocks the 1,25-(OH)2D3-induced increment in cytosolic calcium, but does not block the 1,25-(OH)2D3-induced maturational changes in HL-60 cells. The data suggest that 1,25-(OH)2D3 but not 24,25-(OH)2D3 increases cytosolic calcium in HL-60 cells within 5 min and the increment is due to increased influx of calcium. 1,25-(OH)2D3 modifies membrane permeability to calcium independent of calcium channels sensitive to nifedipine. Finally, 1,25-(OH)2D3-induced maturational changes in HL-60 cells can take place without an increase in cytosolic calcium.
mesh_terms: D000634:Aminoquinolines; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005456:Fluorescent Dyes; D006801:Humans; D009543:Nifedipine / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured
chemical_list: D000634:Aminoquinolines; D005456:Fluorescent Dyes; D002117:Calcitriol; D009543:Nifedipine; C035739:Quin2; D002118:Calcium; D004121:Dimethyl Sulfoxide