FIGURE 1.

Histamine triggers intracellular calcium mobilization in HUVECs. A–C, representative intracellular free Ca²⁺ recordings ([Ca²⁺]_i, mean ± S.E.) show cytosolic Ca²⁺ levels coupled to histamine stimulation. The top bars indicate the type of extracellular solutions (supplemental Table S1) applied to the cells, and the vertical lines on the x axis indicate the time of solution change. Histamine was applied at concentration 1 μm (A, n = 33 cells), 10 μm (B, n = 30 cells), and 100 μm (C, n = 32 cells). D–F, representative [Ca²⁺]_i traces illustrate cellular response to histamine in the absence of extracellular Ca²⁺ (D, n = 45 cells; E, n = 38 cells; and F, n = 25 cells). G, averaged peak value of [Ca²⁺]_i, with or without extracellular Ca²⁺, in response to various concentrations of histamine were summarized. H, averaged sustained value of [Ca²⁺]_i were obtained at 4 min after application of histamine.