Changes in cAMP metabolism during phagocytosis of S. aureus by human monocytes

Involvement of cyclic adenosine 3',5'-mono-phosphate (cAMP) in the phagocytosis of staphylococci by human monocytes was demonstrated by assay of adenylate cyclase and cAMP phosphodiesterase (PDE). Monocyte adenylate cyclase and PDE activities were assayed on cell homogenates prepared from monocytes isolated by plate adherence. Phagocytosis of staphylococci was associated with diminished adenylate cyclase activity, which reached a minimum after 10 min of incubation (p less than 0.05), and an increase in PDE activity (p less than 0.005). Transmission electron microscopy provided evidence that these changes coincide with peak phagocytic activity occurring between 10 and 20 min after the start of phagocytosis but could not be assigned to a particular stage in the phagocytic process.