Abstract
In a recent study on the conjugation of benzoic acid in man, the author found that the excretion of hippuric acid proceeded at a constant rate irrespective of the amount of sodium benzoate administered. 1 Since it was further found that the output of hippuric acid was greatly increased by feeding glycine or foods rich in glycine such as gelatine, it became obvious that the rate of hippuric acid formation is dependent upon the speed with which the body can synthesize glycine. It was determined that a normal adult can produce enough glycine to conjugate from 0.90 to 1.30 gm. of benzoic acid per hour.
Since the main site of the synthesis of glycine is presumably the liver, it was considered probable that certain types of liver damage might show a diminution in the hourly excretion of hippuric acid. On this basis a test was carried out as follows: 5.9 gm. of sodium benzoate dissolved in 150 cc. of water is administered 1 hour after a breakfast consisting of coffee and toast. Complete hourly specimens of urine are collected for 4 hours. Hippuric acid is determined by the author's method. 2 A simpler method which is sufficiently accurate for clinical purposes can be employed. In this procedure the hourly specimen is measured, transferred to a small beaker, and acidified with concentrated HCl until acid to Congo red. (1 cc. of the acid is usually sufficient.) The solution is vigorously stirred until the hippuric acid has completely crystallized out, and then is allowed to stand at room temperature for 1 hour. The hippuric acid is filtered off on a Buchner funnel or a small filter plate, washed with cold water, allowed to air dry, and finally weighed.
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