Effects of various PKC inhibitors on stimulation of basophil histamine release by PMA (panel A), ionomycin (panel B), anti-IgE antibody (panel C), and FMLP (panel D). In each panel, basophils obtained by single step Percoll (low purity) were first incubated with the inhibitor for 10 minutes before the addition of the stimulus. After a 45-minute challenge the supernatants were harvested for histamine analysis. Each panel represents the average of five experiments for each stimulus, (○) bis-indolylmaleimide I, (•) bis-indolylmaleimide II, (▪) Ro 31-8220, (□) Go 6976, and (⧫) calphostin C. Control release averaged 58%, 73%, 38%, and 32% for PMA (30 ng/mL), ionomycin (0.5 μg/mL), anti-IgE antibody (0.2 μg/mL) and FMLP (1 μmol/L), respectively.