Fig. 4.

Inhibition of histamine release by Zn²⁺. Histamine release induced by 0.3 μg/ml anti-IgE (●) or 60 nM PMA (□) in the presence of various concentrations of ZnCl₂, normalized to release in the absence of ZnCl₂. Each value is the mean ± SEM of measurements in three to five experiments using blood from different donors. Spontaneous release was 10.0 ± 0.9% (mean ± SEM, n = 5) of total histamine content (range 7.7–12.9%), the PMA stimulated release was 65 ± 7% (42–82%, n = 5 except n = 3 at 10 μM Zn²⁺), and the anti-IgE stimulated release was 24 ± 6% (13–34%, n = 3). The values for the two stimuli at 30 μM and 100 μM differ significantly (P < 0.001 and P < 0.05, respectively, by Student's t test).