Stem cell factor (SCF) is a ligand for c-kit receptor and has a critical role in the development of mast cells. In this study, we investigated the effect of a panel of kinase inhibitors on SCF-induced histamine release from rat peritoneal mast cells. Genistein, an inhibitor of tyrosine kinases, inhibited SCF-induced histamine release with IC 5 0 of 1.6 x 10 - 5 M. Wortmannin, an inhibitor of phosphatidylinositol 3'-kinase (PI3 kinase), inhibited histamine release stimulated with SCF dose-dependently with IC 5 0 of 4 x 10 - 9 M. KT5926, an inhibitor of myosin light chain (MLC) kinase, reduced histamine release with IC 5 0 of 1.8 x 10 - 7 M. Staurosporine, an inhibitor of protein kinases, also inhibited SCF-induced histamine release with IC 5 0 of 6.5 x 10 - 8 M. These results show the early involvement of tyrosine kinase and PI3 kinase and the possible role of MLC kinase in the late secretory phase in the signaling pathway used by SCF.