Inhibition of the nerve growth factor-induced neurite outgrowth by specific tyrosine kinase and phospholipase inhibitors.

The effects of nerve growth factor (NGF) on PC12h cells have been studied with reference to the relationship between neurite outgrowth and the activities of the enzymes involved in signal transduction in the early stage of NGF action. Pretreatment of cells with selective inhibitors of tyrosine kinase (ST638 and genistein) and phospholipases C (neomycin B) and A2 (p-Bromophenacyl bromide; BPB and indomethacin) depress neurite outgrowth following 60 min treatment with NGF (0.1 microgram/ml). The inhibitor of intracellular calcium mobilization, TMB-8, also significantly depresses the NGF-induced neurite outgrowth. Arachidonic acid release, induced by NGF, from the cell lipids is reduced following previous inhibition of above mentioned enzymes. Based on these results, it is suggested that NGF requires tyrosine kinase in its early stage of action (within 60 min) in PC12h cells, phospholipases C and A2 to release Ca2+ from intracellular stores and arachidonate from cellular phospholipids, in order to induce neurite outgrowth.