Unique deposits in mast cells fixed with pyroantimonate osmium tetroxide

Abstract

Evidence for a unique cation distribution in mast cells in a variety of tissues was obtained by fixation with a modification of the potassium pyroantimonate-osmium tetroxide procedure of Komnick. Fine antimonate deposits with a heterochromatin distribution were abundant in nuclei of other cell types but were diminished to absent in mast cell nuclei. Nuclei of mast cells usually contained large coarse precipitates which measured 100–150 nm in diameter and were distributed peripherally, as well as less coarse deposits, which measured about 50 nm, and were distributed throughout the nucleus. Cytoplasmic deposits distributed in Golgi vesicles, between granules and at the plasmalemma were observed in some cells. It is suggested that these unusual deposits result from precipitation of antimonate by histamine or by cations whose distribution is affected by the highly ionic materials present in mast cells. Mast cells of man differed from those of rodents in containing cytoplasmic lipid droplets with peripheral antimonate deposits.