Cytochemical identification of oxalosuccinic acid in human leukocytes

The anthraquinone dye alizarine red S produced a unique red crystalline precipitate with oxalosuccinic acid. By chemical, colorometric and spectrophotometric analysis, this red precipitate was found to be a salt composed of these two substances, and to be insoluble in hydrochloric acid above pH = 3.2. Other biologic substances producing a red color without the formation of precipitates showed a disappearance of the red color and resumption of the yellow color of alizarine red S above pH = 3.8. On the basis of these observations, a cytochemical test was developed that may identify the site of oxalosuccinic acid in the cytoplasm of peripheral blood leukocytes. Because of the initimate association of oxalosuccinic acid with isocitric dehydrogenase, the test may also indicate the site of this enzyme as well.