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

Abstract

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 ec50 value of 0.5 μM. 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-((17β-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 La3+. 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 Ca2+ influx.