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Article
July 1939

CITRIC AND MALIC ACIDS OF THE OCULAR TISSUES

Author Affiliations

CHICAGO
From the Department of Surgery, Division of Ophthalmology, University of Chicago.

Arch Ophthalmol. 1939;22(1):66-72. doi:10.1001/archopht.1939.00860070082004
Abstract

For a long time it has been known that citric and malic acids take part in the general organic acid metabolism of plants and animals. Recent investigations suggest that the oxidation of citric acid in muscle and many other tissues passes through the following consecutive stages : citric acid → isocitric acid → oxalosuccinic acid → alpha-ketoglutaric acid → succinic acid → fumaric acid → levomalic acid → oxaloacetic acid → citric acid. It appears that the citric acid cycle is one way by which carbohydrate is oxidized in muscle tissue. There is reason to believe that a similar metabolic process occurs in ocular tissue.

The interest in the past has been mainly centered on the amount of citric acid in the intraocular humors. In 1927 Ahlgren1 found a citric acid dehydrogenase in lens. Two years later Grönvall, using the method of Thunberg, noted that citric acid is a normal

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