MATERIALS AND METHODS

endocytic vacuole, the phagosome. Various techniques have been used to compare the composition of phagosomal membrane with the plasma membrane. Studies have shown, for example, that the two membranes are not identical with respect to iodinated proteins [39], carrier-mediated transport [31,321, concanavalin A binding sites [22], viscosity [3], and lipid composition [25]. The enzyme 5’-nucleotidase (5’NT), which is either present in free form in fluids such as serum [18], or cell-associated, has been shown to be present on guinea pig exudate PMN [12,13]: as an ectoenzyme, 5’NT is an intrinsic glycoprotein anchored in the lipid bilayer of the membrane [14,21], with its active site facing the external medium. In the present study, we used a cytochemical method to mark the 5’NT activity on guinea pig exudate PMN and then followed the distribution of the enzyme during the early stages of phagocytosis. 5’NT was shown to be largely absent from the secondary lysosomes. Using biochemical techniques, we confirmed the nonrandom distribution of 5 ’ NT in the phagosomal membrane compared to the plasma membrane of guinea pig PMN