The pulmonary-alveolar macrophage lies in direct contact with inhaled bacteria and airborne pollutants and is therefore the primary phagocytic cell responsible for destruction and/or removal of these contaminants. Experiments on the initiation of the in vitro stimulated O2 associated reactions by the alveolar macrophage will be conducted since there is increasing evidence that these O2 reactions are involved in the microbiocidal activity of these cells. The initial events involved in the stimulation by n-formyl-methionlyphenylalanine and concanavalin A (soluble stimulating agents) and latex beads (phagocytic stimulating) of O- production in alveolar macrophages will be examined. Intracellular concentrations of Na ion, K ion, Ca ions and Mg ions will be determined in control and stimulated cells. Plasma membrane fluxes of each of the cations will be measured for control and stimulated cells by following both the influx and efflux of Na22 ion, K42 ion (Rb86 ion), Ca45 ion and Mg28 ions in alveolar macrophages. Particular attention will be made to the proposed regulatory role of cytosolic levels of free Ca ions and possible sequestration (binding) by organelles. Changes in ion permeabilities and/or ion concentrations would be reflected in changes in the transmembrane electrical gradient. Therefore, the equilibrium distribution of (H3)-tetraphenylphosphonium will be used to measure the plasma transmembrane electrical gradient, allowing for corrections due to binding and compartmentation of the probe, in control and stimulated cells and correlated to the cation concentration and flux measurements. The energy state of the alveolar macrophage will be measured (metabolism rates, (ATP)/(ADP)(Pi) and (NADH)/(NAD)) to determine if changes in the energy state occur early in the stimulation of O2 production, possibly linked to an ATPase. The temporal and causal sequence of the initial events that lead to O2 production will be established, in both guinea pig and human alveolar macrophages.