Inhibitory effects of azelastine on protein kinase C and diphosphoinositide kinase in rat mast cells.

Rat mast cells purified on a Percoll gradient were challenged with compound 48/80 and protein kinase C activity in the cell pellets and the amount of histamine release into the supernatant was assayed by measuring the incorporation of 32P from [gamma 32P]ATP (adenosine triphosphate) into lysine-rich histone and by the fluorometric technique, respectively. In another series of experiments, rat mast cell granules were isolated in a gradient from sonicated rat mast cells and diphosphoinositide kinase activity was assayed by measuring the incorporation of 32P from [gamma 32P]ATP into triphosphoinositide on oxalic acid-impregnated silica gel plates after the extraction of lipids in acidic condition. Azelastine (A-5610, E-0659) inhibited the histamine release from the cells in parallel with the tendency to inhibit the increased protein kinase C activity in the activated mast cells. Azelastine also inhibited the diphosphoinositide kinase activity in the granules. These inhibitory effects of azelastine on the phosphorylation enzymes in rat mast cells may be involved in the inhibitory mechanism of the mediator release from the cells.