A HISTOCHEMICAL EVALUATION OF THE PYROANTIMONATE-OSMIUM REACTION

Abstract

The chemical nature of the pyroantimonate-osmium (PAO) reaction in normal human bone marrow cells has been evaluated by the application of a number of digestion and blocking procedures as well as the electron microprobe. Five foci of reactivity are localized in cells fixed directly in the PAO reagent, viz., nucleoli, heterochromatin, cytoplasmic granules, particulate glycogen and the outer plasmalemmal surface. Heterochromatin and nucleolar staining are attributable to calcium bound to nucleic acids as well as to reactive amino groups on histones. Granule staining is dissociable into acid-dialyzable, ribonuclease (RNase)-stable and RNase-labile components but sulfate groups of acid mucosubstances are probably not involved. Glycogen staining by the PAO reagent has been verified and shown to result from the formation of organometallic complexes between the pyroantimonate ion and the C2-C3-free hydroxy groups of the glucose residues. PAO reactivity has been definitely localized along the outer plasmalemmal surface, but this component of PAO staining is resistant to all control measures employed. These studies have illustrated the complexity and polyvalency of the PAO reaction and have shown that PAO staining is not exclusively associated with metallic cation localization.