Histochemical detection of l-gulonolactone: phenazine methosulfate oxidoreductase activity in several mammals with special reference to synthesis of vitamin C in primates

Summary An improved detection of activity of l-gulonolactone oxidase, which is responsible for the final oxidative step in the synthetic process of l-ascorbate from glucose in animals, was achieved using phenazine methosulfate and cyanide. Cold acetone fixation eliminated non-specific deposition of formazan on lipid droplets. The specificity of the method was tested and proven by a biological control, histochemical controls, inhibitors and activators. By application of the method, strong reactivity was found in the cytoplasm of centrilobular parenchymal cells of livers of the opossum, rat, ground squirrel and flying squirrel. Staining of dog liver was moderate and centrilobular. Prosimians were strongly positive: The centrilobular localization was found in the tree shrew and galago; slow lorises and some pottos showed strong reactivity in centrilobular cells and some peripheral cells as well. These prosimians seem to be able to synthesize l-ascorbate as many lower mammals are. On the contrary, true simians (i.e. the squirrel monkey, spider monkey, rhesus monkey and chimpanzee) were negative as guinea pigs were, suggesting their probable inability for l-ascorbate synthesis.Visiting scientist from the Department of Anatomy, Tokyo Medical and Dental University, Tokyo, Japan.T. R. Shanthaveerappa in previous publications, also fellow, Department of Anesthesiology, Emory University.