Electron microscopic cytochemical studies have been made on sulfated glycosaminoglycans in mast cell granules from the rat peritoneal cavity by means of combined alcian blue (AB) pH 1.0-phosphotungstic acid (PTA) staining and enzyme (heparinase or chondroitinase ABC) digestion or chemical modification (nitrous acid) procedures. The results obtained revealed that the mast cell populations from the rat peritoneal cavity are grouped into at least three cell types on the basis of the molecular species of sulfated glycosaminoglycans contained in the cytoplasmic granules, the first cell type occupying the majority of the cell population with cytoplasmic granules containing primarily heparin, the second cell type being of an exceedingly small proportion with cytoplasmic granules containing primarily isomeric chondroitin sulfate (D and/or E), and the third cell type (intermediates between the first and second types) constituting a relatively small proportion with cytoplasmic granules containing two kinds of cytoplasmic granules containing heparin and isomeric chondroitin sulfate (D and/or E) respectively. In addition, unique substructures of cytoplasmic granules containing different sulfated glycosaminoglycans were disclosed such as tubular or thin thread-like elements, interstitial vesicles and surface spine-like figures.
The present results are taken to represent the first electron microscopic cytochemical evidence that mast cell populations are heterogeneous in terms of molecular species of sulfated glycosaminoglycans contained in the cytoplasmic granules in mammals.