Mechanisms of histamine-induced intracellular Ca2+ release and extracellular Ca2+ entry in MG63 human osteosarcoma cells

The effect of histamine on intracellular free Ca2+ levels (Ca2+](i)) in MG63 human osteosarcoma cells was explored using fura-2 as a Ca2+ dye. Histamine increased (Ca2+](i)) in a concentration-dependent fashion with an EC(50) value of 0.5 microM. Extracellular Ca2+ removal inhibited the (Ca2+](i)) signals. Histamine failed to increase (Ca2+](i)) in Ca2+-free medium after cells were pretreated with thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor). Addition of Ca2+ induced concentration-dependent (Ca2+](i)) increases after preincubation with histamine in Ca2+-free medium. Histamine-induced intracellular Ca2+ release was abolished by inhibiting phospholipase C with 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). The (Ca2+](i)) increase induced by histamine in Ca2+ medium was abolished by cimetidine, but was not altered by pyrilamine, nifedipine, verapamil, and La(3+). Together, this study shows that histamine increased in (Ca2+](i)) in osteosarcoma cells by stimulating H2 histamine receptors. The Ca2+ signal was caused by Ca2+ release from the endoplasmic reticulum in a phospholipase C-dependent manner. The Ca2+ release was accompanied by Ca(2+) influx.