Ascorbic acid in the eye-lens and aqueous humour of the ox.

IN an earlier communication [Birch and Dann, 1933] on the estimation and distribution of ascorbic acid and glutathione in animal tissues we drew attention to the distribution of ascorbic acid in organs other than the suprarenal cortex, as detected by the indophenol reagent. The presence in a number of tissues of reducing substances other than glutathione had become evident from the work of Mason [1930] and of Bierich and Rosenbohm [1933], but no evidence of the identity of such substances had been obtained. By applying the indophenol titration for ascorbic acid to tissue extracts we were able to demonstrate the presence of the acid in a number of organs and to give figures for the amounts present. At the same time it was pointed out that the indophenol titration may not be specific for ascorbic acid in tissue extracts, so that other tests are necessary to confirm the results obtained by the titration method. The silver nitrate staining test was applied to a number of the tissues which had been found by means of the indophenol titration to contain ascorbic acid, with results which were not always in harmony with those obtained by the latter method. Some tissues found by the titration method to contain ascorbic acid gave little or no staining with silver nitrate, and led us to the conclusion already formulated by Harris and Ray [1933, 1] that a positive result with this test indicates the presence of ascorbic acid in a tissue but a negative result does not necessarily mean that ascorbic acid is absent. In order to examine the reliability of results obtained by the titration method it was decided to carry out biological assays of the ascorbic acid found by the titration method to occur in unexpected sites. The tissues chosen for examination were the eye-lens and aqueous humour of the ox.