Abstract
Changes in cytosolic Ca2+ concentration ([Ca2+],) in cultured human mucosal microvascular endothelial cells (HM-MECs) from nasal inferior turbinate were measured using a fluorescent Ca2+-sensitive dye, fura-2, and photometric fluorescence microscopy. Histamine caused a transient increase in intracellular free Ca2+ in cell populations and in individual cells, followed by a decrease to a sustained elevation. Histamine (100 μ) elevated [Ca3+]i in HMMECs up to 563 ± 20 nM from a resting level of 60 ± 45 nM (means ± SD, n = 31). Promethazine (a histamine H, receptor antagonist) inhibited [Ca2+] increase during histamine stimulation, whereas cimetidine (a H2 receptor antagonist) and thioperamide (a H, receptor antagonist) showed no inhibition. These results suggest that the histamine increase [Ca2+]i in HMMECs induces both a Ca2+ release from stores and a Ca2+ influx through activation of the H, receptor.
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