Ultrastructure of proteoglycans in the specific granules of guinea-pig basophilic leukocytes as demonstrated by cuprolinic blue staining

A barium method for the cytochemical detection of sulfated glycosaminoglycans in mast cells and basophilic leukocytes

Barium ions precipitate inorganic as well as organic sulfate compounds and they can be detected by a reaction with sodium rhodizonate. In this work, we describe the use of a barium method for the selective demonstration of sulfated glycosaminoglycans in cytoplasmic granules of mast cells and basophilic leukocytes. Methanol-fixed smears of mouse peritoneal mast cells and rat bone marrow basophils were treated with 5% BaCl2 for 10 min, followed by staining with either 0.2% sodium rhodizonate in 50% ethanol for 2 h at 60 degrees C, or 0.01% brilliant green in distilled water for 1 min. Light microscopic observation revealed a strong staining reaction of the cytoplasmic granules of these cell types, which was more selective when using sodium rhodizonate. Control smears treated with BaCl2 or sodium rhodizonate alone, and those subjected to methylation/extraction of sulfate groups before staining remained unstained. The selective binding of barium ions to mast cell granules was established with scanning electron microscopy using a backscattered electron detector, and confirmed by energy dispersive X-ray microanalysis as well as element mapping.