The fate of plasma membrane macrophage enzyme markers during endocytosis of Trypanosoma cruzi.

The enzyme activity of Na+-K+-ATPase, Mg++-ATPase, 5'-nucleotidase and adenylate cyclase was cytochemically detected, at the ultrastructural level, in normal mouse peritoneal macrophages Trypanosoma cruzi. Reaction product, indicative of the enzyme activity, was seen in association with the plasma membrane of the macrophage, showing an homogeneous distribution. No reaction product indicative of Na+-K+-ATPase, Mg++-ATPase or adenylate cyclase activity was seen within the cell. Reaction product, indicative of 5'-nucleotidase activity, was seen in cytoplasmic vacuoles. Macrophages incubated in the presence of T. cruzi ingest this parasite which can be seen within membrane-bounded cytoplasmic vacuoles (phagosomes). No activity of the plasma membrane-associated enzymes was seen in the membrane lining vacuoles containing parasites. This observation, together with others previously reported, suggest that the macrophage possesses mechanisms which determine the components of the plasma membrane which are interiorized during the process of endocytosis.