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The cardinal role of the liver in protein and amino acid metabolism has been well established. Consequently, studies of amino acid metabolism occupy a natural and fundamental place in an investigation of metabolic aberrations in hepatic disease. In 1913, Van advantage since this serves as a "label" in the interpretation of the metabolic fate of the administered methionine.In the present study a standard dose of DLmethionine was administered intravenously. Observations were then made on the rate of disappearance of the amino acid from the plasma together with a comparison of the excretion of free methionine and sulfate sulfur before and after the substance was given. Since the racemic DLmethionine was used, it was of interest to follow the metabolism of both isomers. This was made possible by the separate analysis of samples by two micro-organisms, one utilizing only the Lisomer, the other, both D-and L-isomers. METHODSAll patients (veteran and naval personnel) received a standard high protein, high carbohydrate intake over a two-day period preceding the test, during which time all medication was discontinued. They received no food from 8:00 p.m. the preceding night until after the 180-minute blood and urine samples had been obtained. Methionine determinations were made on deproteinized filtrates of plasma obtained from heparinized blood. After removal of a blood sample for determinations of the fasting methionine level, 50 cc. of a 3 per cent DLmethionine solution were injected over a five-minute period. Blood samples were then drawn at 15, 30, 60, 120, and 180 minutes after the injection. Urine samples corresponding to a two-hour period prior to the administration of the test dose of methionine as well as to the subsequent three-hour period were collected and assayed for methionine and, in some cases, sulfate sulfur (both free and total), and total amino nitrogen. This latter constituent will be discussed in a later communication. In several instances, methionine excretion during various periods up to 48 hours after the test dose had been given was measured.Methionine was determined microbiologically using as test organisms Leuconostoc mesenteroides, P-60, for the assay of L-methionine and Lactobacillus fermenti, 36, for 677

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