Cytochemical Analysis Of Spatial Structure Of Glycogen Molecules In Rat Hepatocytes

Abstract It is currently thought that a full glycogen molecule (β-particle) has a spherical shape with 12 concentric tiers of glucose residues with glycogenin in the center and diameter of about 42 nm. However, the spatial structure of the β-particle remains poorly understood. In this study, the structure of glycogen β-particles in hepatocytes of starved and fed rats has been studied using in situ cytofluorometry technique and measurement of speed of glycogen staining with the Schiff's reagent. Based on the results of these measurements we suggest a novel model of spatial structure of glycogen molecules in which quickly stained, labile fraction of glycogen (LF) represents residues located at the internal tiers of the molecule, while slowly stained, stable fraction of molecule (SF) represents residues at the external tiers of the molecule and associated with proteins. This model predicts that in the starved rats the 3rd and 4th tiers glucose residues (42% of all) are bound to proteins. In the fed rats on 7th and 8th tiers together ∼19% of glucose residues were bound to proteins. The external tier of glycogen molecules was never free of proteins and the enzyme amount on the particle surface was variable. Thus, using this cytofluorometry method makes it possible to study the spatial structure of glycogen in situ and to obtain data on its features in this particular cell.