A Reducing Substance in Brain Tissue


EXPERIMENTS in this laboratory on the chemical basis of some histological staining reactions of brain tissue have shown that all the brain tissues examined (mouse, rat, guinea pig, ox) contain a substance which has the peculiar property of reducing silver nitrate in neutral or acetic acid solution at room temperature, although ammoniacal silver nitrate is not readily reduced in the cold. Extracts of brain tissue containing this substance reduce phenol 2: 6 dichloro-indophenol under the conditions described by Harris and Ray1 and Birch, Harris and Ray2 for the estimation of ascorbic acid in tissues, and aqueous alcoholic extracts of ox brain tissue contain the reducing equivalent of 12—15 mgm. of ascorbic acid per equivalent of 100 gm. of tissue, as determined by this method. But the general properties of this substance (or substances) clearly differentiate it from ascorbic acid, as shown in the following table: Daily doses of ox brain extract containing the reducing equivalent of 6 mgm. of ascorbic acid failed to prevent the appearance of the symptoms of scurvy in guinea pigs fed on a scorbutic diet, and it is clear that estimations of ascorbic acid in brain tissue by the indophenol titration method yield fallacious results.

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  1. 1

    Harris and Ray, Biochem. J., 27, 303; 1933.

  2. 2

    Birch, Harris and Ray, ibid., 27, 590; 1933.

  3. 3

    Boyland, ibid., 27, 802; 1933.

  4. 4

    Harris, NATURE, 132, 605; Oct. 14, 1933.

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