A B S T R A C T Isolated neutrophilic leukocytes were incubated with primary amines and related nitrogenous compounds. Stimulation of neutrophil oxygen (02) metabolism with phorbol myristate acetate or opsonized zymosan resulted in production of hydrogen peroxide (H202), myeloperoxidase-catalyzed oxidation of chloride (Cl-) to hypochlorous acid (HOCI), and the reaction of HOC1 with the added compounds to yield nitrogen-chlorine (N-Cl) derivatives. Formation of NCl derivatives of low lipid solubility resulted in accumulation of the derivatives in the extracellular medium. These oxidizing agents were identified and measured on the basis of their absorption spectra and their ability to oxidize 5-thio-2-nitrobenzoic acid to the disulfide form. The yield of N-Cl derivatives was in the order: taurine > Tris > spermidine > spermine > glucosamine > putrescine > guanidinoacetate. Accumulation of N-Cl derivatives was also observed in the absence of added amines, owing to the reaction of HOC1 with endogenous taurine and other amines that were released from the cells into the medium.In the presence of compounds that yield lipophilic N-Cl derivatives, little or no accumulation of oxidizing agents was observed. Instead, these compounds inhibited the accumulation of N-Cl derivatives that was obtained with taurine, and their effect was competitive with taurine. Inhibition was in the order: methylamine > ethanolamine > phenylethylamine > p-toluenesulfonamide > ammonia > guanidine. Formation of lipophilic N-Cl derivatives also resulted in inhibition of 02 uptake and glucose metabolism. Inhibition was prevented by adding catalase to eliminate H202, dapsone to inhibit myeloperoxidase, taurine to compete for reaction with HOC1, or compounds that are rapidly oxidized by HOC1 or N-Cl derivatives, to reduce these Received for publication 19 January 1983 and in revised form I April 1983. oxidizing agents. The results indicate that: (a) formation of N-Cl derivatives that do not penetrate biological membranes can protect leukocytes against the cytotoxicity of HOC1 and lipophilic N-Cl derivatives, and (b) formation of membrane-permeable N-Cl derivatives in the absence of target cells or readily oxidized substances results in oxidative attack by the NCl derivatives on leukocyte components and inhibition of leukocyte functions.