Figure 3. Concentration-dependent effect of bradykinin (BK) on mobilization of [Ca²⁺]_i in normal, primary h-CM cells. Fluorescent dye-loaded h-CM cells were exposed to different concentrations of BK and the changes in relative fluorescence units (RFUs), indicating changes in levels of [Ca²⁺]_i, monitored over time (Figure 3A). The peak responses to various BK concentrations were then used to construct the concentration-response curves. Other BK-related peptides were tested in the same manner and their concentration-response curves plotted (e.g., data from a representative experiment; Figure 3B). Agonist potency data from many such experiments were obtained and are shown in Table 1 as mean ± SEM of EC₅₀ values (n=3–7). The effects of a peptide B₂-receptor antagonist (HOE-140; Figure 3C) and a non-peptide antagonist (WIN-64338; Figure 3D) on BK (10 nM)-induced elevation of [Ca²⁺]_i were also determined, and antagonist potencies derived (Table 1, lower section).