Abstract
The subcellular route of incorporation of complex carbohydrates into rabbit heterophil primary granules and their subsequent intragranular distribution during granule maturation were studied with ultrastructural, cytochemical, and radioautographic methods. High iron diamine (HID) staining of sulfated glycoconjugates in primary granules was partially diminished after treatment with chondroitinase ABC or after removal of N-sulfate groups with nitrous acid, but was not altered by exposure to hyaluronidase, trypsin, or HCl. Subsequent thiocarbohydrazide-silver proteinate (TCH-SP) straining of thin sections increased the density of the HID reaction product. Golgi-derived spherules and very immature morular granules stained weakly with HID-TCH-SP and labeled intensely after a 10 min incubation with 35SO4. After a 60 min 35SO4 pulse and a 60 min chase, an increase in radiolabeling was observed in granules with HID stained, fused morular material, and some labeling was present in more mature rim stained granules. Fully mature granules lacked HID or HID-TCH-SP staining, but contained most of the 35SO4 labels after a 60 min pulse and 18 hr chase in vitro. Periodate-thiocarbohydrazide-silver proteinate (PA-TCH-SP) staining of unosmicated thin sections localized vicinal glycol-containing complex carbohydrates in Golgi-associated small vesicles. These vesicles lacked HID-TCH-SP staining and apparently contained neutral glycoprotein. They frequently bordered, in a rosette arrangement, the immature morular granules, but not the more mature primary granules. The PA-TCH-SP method localized complex carbohydrates in the rim of granules precursors and enclosed a spherule or morula, but failed to stain the sulfate-containing material in the morulas or spherules. PA-TCH-SP reactivity was diffusely distributed in moderately mature granules and was decreased in fully mature granules. These results indicate that heterophil primary granule contain several complex carbohydrates including O-sulfated and N-sulfated glycosaminoglycans, as well as vicinal glycol-containing glycoproteins. These complex carbohydrates are transported to immature primary granules by different Golgi-derived organelles. The complex carbohydrates are subsequently distributed differently within primary granules and become masked to staining as the granule matures.