Several types of membrane-limited storage granules fill the cytoplasm of mature neutrophil leukocytes. The granules contain an array of enzymes and proteins which appear to play a key role in acidification of phagolysosomes, killing and digestion of phagocytized bacteria and activation of other neutrophils and the perpetuation of inflammation, through secretion of their contents to the extracellular medium. Neutrophils from peritoneal exudates of guinea pigs will be exposed to nitrogen cavitation to selectively rupture their plasma membranes and the intracellular granules will be separated on isosmotic, continuous density gradients of Percoll. The various subtypes of granules will be characterized as to enzyme content and the ionic permeability properties of their limiting membranes. Passive permeability of granule subtypes to protons, cations and anions will be measured by radiochemical and spectrophotometric techniques. The electrochemical gradient of protons (Delta p) which may be developed across the limiting membrane of granules will be assessed by measurements of the pH gradient (Delta pH) and membrane potential (Delta Psi) during incubation plus/minus MgATP. The Delta pH and Delta Psi will be measured by distribution of lipophilic, radioactive weak base or acid (methylamine, DMO) and anion or cation (SCN-, TPMP+), respectively. The role of a H+ pumping ATPase in maintaining Delta pH and/or Delta Psi will be determined using ATPase inhibitors (trimethyltin, DCCD) and agents which selectively collapse Delta pH (NH4+ salts, acetic acid) or Delta Psi (SCN-, valinomycin + K+) or which allow electrochemical equilibration of H+ (FCCP). The possible function of the components of Delta p in maintaining granule stability or initiating chemiosmotic release of contents will be examined. These studies will lead to a better understanding of the properties of neutrophil granules and their function within the cell which is the primary cellular component of the acute inflammatory reaction. Ultimately, the results obtained in these studies will further our knowledge of the role of the neutrophil in a wide variety of inflammatory diseases.
