Electron microscopic localization of chromogranin A in osmium-fixed neuroendocrine cells with a protein A-gold technique.
An antibody (LK2H10) to chromogranin A has been recommended for use in ultrastructural identification of neuroendocrine secretory granules. Previous studies have demonstrated immunoreactive chromogranin A in specimens prepared for electron microscopy by glutaraldehyde fixation only. In this study, the effect of specimen post-fixation by osmium tetroxide on post-embedding localization of chromogranin A was evaluated. Human tissues from benign endocrine glands, neuroendocrine tumors, and non-neuroendocrine tumors were post-fixed in osmium, embedded in epoxy resin, and the sample thin sections immunolabeled using a protein A-gold technique. Chromogranin A-positive neurosecretory granules were detected in pancreatic islets, adrenal medulla, stomach, ileum, anterior pituitary, and parathyroid. Mid-gut carcinoids, bronchial carcinoids, pheochromocytomas, paragangliomas, carotid body tumors, and thyroid medullary carcinomas contained immunoreactive granules. Cytoplasmic granules in non-neuroendocrine tumors did not react for chromogranin A. Tissues post-fixed in osmium tetroxide had optimally preserved ultrastructural features, and use of this fixative is compatible with postembedding localization of chromogranin A in neurosecretory granules.
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D002276:Carcinoid Tumor / Q000378:metabolism; D053379:Chromogranin A; D002864:Chromogranins / Q000032:analysis*; D003594:Cytoplasmic Granules / Q000378:metabolism; D005404:Fixatives; D006046:Gold; D006651:Histocytochemistry; D006801:Humans; D007158:Immunologic Techniques; D007414:Intestinal Neoplasms / Q000378:metabolism; D008854:Microscopy, Electron / Q000379:methods; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009490:Neurosecretory Systems / Q000378:metabolism*; D013205:Staphylococcal Protein A
C506150:CHGA protein, human; D053379:Chromogranin A; D002864:Chromogranins; D005404:Fixatives; D009419:Nerve Tissue Proteins; D013205:Staphylococcal Protein A; D006046:Gold