Lysosomal enzymes of phagocytic cells as humoral mediators of inflammation: modulation of their release by cyclic nucleotides.

The origin of lysosomes in phagocytic cells is described. Studies on their characterization by both morphological and biochemical methods are summarized. Lysosomal enzymes of both polymorphonuclear leukocytes and macrophages can be released by exocytosis in response to a variety of inflammatory stimuli. This response is modulated by cyclic nucleotides. In the polymorphonuclear leukocyte cAMP inhibits enzyme release while cGMP enhances release; the effects of the cyclic nucleotides are less clear in the macrophage. The possible involvement of microtubules and microfilaments in the release process is discussed.