Ultrastructural alterations during ATP-induced secretion of lysosomal enzymes from rabbit polymorphonuclear leukocytes.

Rabbit neutrophils incubated in low-ionic-strength media were stimulated by ATP to secrete lysosomal enzymes. This was greatly enhanced in the presence of cytochalasin B. ATP in these circumstances induced the cell to form large cytoplasmic extensions that were largely devoid of granules. In the presence of both ATP and cytochalasin B, however, the projections contained granules in close proximity to the cell membrane. Neutrophils in low-ionic-strength buffer were capable of binding to zymosan particles coated with C3b but not of phagocytizing them. Release of granule enzymes was observed and exocytosis of granules appeared to occur at sites distant from those portions of the plasma membrane adherent to the particle.