The metabolic basis of phagocytosis. III. Incorporation of inorganic phosphate into various classes of phosphatides during phagocytosis.

Among the metabolic events which have been found to accompany the ingestion of particles by polymorphonuclear leukocytes (1) is an enhanced incorporation of inorganic phosphate-P32 into the total phosphatide fraction (2). Under suitable conditions, there was found to be a doubling of the specific activity of this fraction in leukocytes which were engulfing starch granules, compared with leukocytes at rest (2). We suggested previously (2) that the increased labeling of phosphatides when leukocytes accumulate particles might not be different in principle from that observed during some types of secretion, i.e. when particles or substances in solution pass from the inside of cells to the outside (e.g. pancreatic secretion of zymogen granules (3)). Experiments have now been carried out to determine whether the labeling of speci$c phosphatides is observed during the passage of particles about 1 to 3 p in diameter into leukocytes.