The long term objectives of this application are to define in molecular terms the biochemical and physiological responses of the neutrophil to chemotactic agents. In this work, particular stress is laid upon delineating the nature and role of the formylpeptide chemotactic receptor of the neutrophil but there is also a broadening of the long term objectives to include the study of the terminal mechanisms of neutrophil granule exocytosis. The initial aim is to extend and refine the model of the formylpeptide receptor of the rabbit neutrophil to the area of accommodating a terra, pentapeptides and also longer chain peptides. In addition, particular attention will be paid to the nature of the conformation of the peptide in the receptor using computer simulation to guide the research. In this regard also, the basis for the high activity of the unformulated defivatives of the pentapeptides we have studied will also be investigated. The second aim is to study the nature and mechanism of the release of the specific granule contents in cell free extracts of rabbit peritoneal neutrophils and attempt to extend these studies to the release from azurophil granules and to release engendered by fMet-Leu-Phe-OH stimulation of receptors present in the cell free neutrophil system. The third aim is to test the hypothesis that prior incubation with phorbol 12-myristate 13-acetate (PMA) induces inhibition of neutrophil responses to fMet-Le-phe and other chemotactic factors by activating protein kinase C to phosphorylate the alpha n subunit of Gn the G protein that mediates the stimulated receptor activation of phospholipase C. The putative phosphorylation causes a shift in the equilibrium between alpha n and beta gamma to the undissociated heterotrimer Gn and a loss of Gn function.