A cell-permeable, fungal metabolite that acts as a potent, selective, and irreversible inhibitor of phosphatidylinositol 3-kinase in purified preparations and cytosolic fractions (IC₅₀ = 5 nM). Blocks the catalytic activity of PI 3-kinase without affecting the upstream signaling events. Preincubation of fibroblasts with wortmannin abolishes PDGF-mediated Ins(3,4,5)P₃ formation (IC₅₀ = 5 nM). Also blocks the metabolic effects of insulin in isolated rat adipocytes without affecting the insulin receptor tyrosine kinase activity. Inhibits MAP kinase activation induced by platelet activating factor in guinea pig neutrophils (200 - 300 nM). Also inhibits other kinases such as myosin light chain kinase (IC₅₀ = 200 nM) and PI 4-kinase at concentrations higher than that required for inhibition of PI 3-kinase. Also blocks phospholipase D. A 10 mM (1 mg/233 µl) solution of Wortmannin (Cat. No. 681676) in DMSO is also available.