Release and synthesis of histamine in rat basophilic leukemia (2H3) cells

On the stimulation of rat basophilic leukemia (2H3) cells with an IgE oligomer, the intracellular Ca2+ concentration, which was measured with fura-2 as a fluorescent probe, began to increase after 1 min lag period, reached its maximum at 4 min, and gradually decreased to the original level. The histamine release occurred slightly more slowly than the increase in the intracellular Ca2+. It started 2-3 min after the stimulation, reaching a peak at 6 min and thereafter decreasing slowly. To supplement the released histamine, the activity of histidine decarboxylase, a histamine-forming enzyme, increased 5-fold several hours after the stimulation by an IgE oligomer, and this increase may be mediated by protein kinase C system.