Tissue fixation with diimidoesters as an alternative to aldehydes. II. Cytochemical and biochemical studies of rat liver fixed with dimethylsuberimidate.

Rat liver fixed with dimethylsuberimidate (DMS) was studied to investigate the use of diimidoesters as dixatives for light and electron microscopic cytochemistry. Paraffin sections of liver fixed with DMS at pH 9.5 were weakly stained with the ninhydrin-Schiff procedure, indicating extensive reaction of NH3+ groups with the fixative. Nuclei were strongly strained by the Feulgen procedure, with no background [corrected] reaction. In contrast, glutaraldehyde fixation resulted in a significant background reaction in the cytoplasm and nuclei in controls for the Schiff-based stains. DMS-fixed liver stained intensely for glycogen with the Periodic acid-Schiff procedure, and biochemical analysis of glycogen retention and extractability indicated that DMS retained considerably more glycogen in sections than glutaraldehyde. DMS-fixed liver incubated for thiamine pyrophosphatase activity revealed reaction product in ER cisternae, Goli saccules and bile canaliculi. Peroxisomes were strongly reactive for catalase activity after incubation in diaminobenzidine medium, and reaction product of glucose-6-phosphatase activity was considerably greater following DMS fixation than after glutaraldehyde. Biochemical studies revealed up to twice as musch residual activity of glucose-6-phosphatase after DMS fixation. These results suggest that DMS may be useful as a primary fixative for certain cytochemical procedures.