Ultrastructural cytochemistry of carbohydrates in microfibrils associated with the amorphous elastin in the monkey aorta

Two distinct ultrastructural components of elastic fibers can be identified--namely, the amorphous elastin and the microfibrils. We have examined the tunica adventitia of monkey aortas to demonstrate differential localization of carbohydrates in elastic fibers and collagen fibrils using Thiéry's periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) staining of thin sections for vicinal-glycol-containing complex carbohydrates, en bloc concanavalin A (Con A) staining specific for alpha-D-mannosyl and alpha-D-glucosyl groups, and en bloc wheat germ agglutinin (WGA) staining specific for N-acetyl-D-glucosamine, N-acetylneuraminic acid, and N-acetyl-D-galactosamine. The PA-TCH-SP method moderately stained microfibrils and weakly stained collagen fibrils, but did not stain the amorphous elastin. Both Con A and WGA staining methods strongly stained microfibrils and moderately stained collagen fibrils, whereas the amorphous elastin lacked staining. Thus PA-TCH-SP, Con A, and WGA staining methods allow differential ultrastructural localization of carbohydrates in elastic fibers and collagen fibrils in monkey aortic adventitia and demonstrate the presence of more carbohydrate components in microfibrils than in collagen fibrils, whereas amorphous elastin lacks carbohydrate staining.