Changes in protein kinase C activity during histamine release from activated rat mast cells

Rat mast cells were challenged with compound 48/80 or calcium ionophore A23187, and protein kinase C activity in the cell pellets and the amount of histamine release into the supernatant were measured. After stopping the reaction, rat mast cells were lysed in a medium which prevents alterations in phosphorylation and dephosphorylation during sample processing. Histamine was significantly released from compound 48/80-stimulated mast cells at 30 s after the stimulation. In parallel with this, protein kinase C activity in the cell pellets increased at 30 s and 1 min and returned to basal value 3 min after the stimulation. When mast cells were incubated with various concentrations of 48/80 for 30 s, the amount of histamine release and protein kinase C activity increased dependently on the concentration of 48/80. Significant histamine release from A23187-stimulated mast cells was found at 1 min after the stimulation. Also protein kinase C activity in the cell pellets increased at 1 min and returned to basal value 5 min after the stimulation. A reduction of cytosolic protein kinase C activity was observed upon 48/80 treatment in a time- and concentration-dependent manner. Further, staurosporine, a potent inhibitor of protein kinase C, inhibited 48/80-induced histamine release in parallel with the inhibition of protein kinase C activity. These findings suggest that transient increase of protein kinase C activity may be involved in the mast cell activation process.