Glycogen granules in resting and inflammatory rainbow trout phagocytes - an ultrastructural study

The ultrastructural image of glycogen granules in the cytoplasm of rainbow trout phagocytes in sections stained by the conventional lead or uranyl-lea d stains is highly dependent on fixation conditions, the granules being vis ible only when adequate fixation protocols are used. Morphometry of samples processed for the detection of peroxidase or esterase activities (to speci fically label neutrophils and macrophages, respectively), and simultaneousl y stained for the specific detection of glycogen, showed that inflammatory peritoneal neutrophils were richer in glycogen granules than resting neutro phils. This increase in glycogen content occurs after the migration from th e haematopoietic tissues and peripheral blood to the inflamed foci. Glycoge n granules could not be found in resting peritoneal macrophages but were fo und in inflammatory macrophages. The macrophage granules occurred in smalle r amounts than in neutrophils, and consisted of granules identical to those of neutrophils together with significantly smaller granules. No evidence f or the utilization of glycogen by neutrophils phagocytosing bacteria within the peritoneal cavity was found.