Amino Acid Metabolism. Fate of dl-Methionine in the Phlorhizinized Dog

Abstract

The manifest interest in the metabolism of methionine makes it desirable to record the fate of this amino acid in phlorhizin diabetes. The generalizations to be derived from the fate of other amino acids (Lusk 1 ) leads one to suspect that methionine can act as a glucose former. The data to be presented indicate that dl-methionine can be metabolized to yield glucose in the phlorhizinized dog.

dl-Methionine was synthesized by the method of Windus and Marvel.^∗2 Phlorhizin was administered by the Coolen 3 method. Urine was collected by catheterization. Nitrogen was determined by the usual Kjeldahl method, glucose by the Benedict method as described by Quick, 4 and sulfur and sulfates by the methods of Folin. 5 The amino acid was administered as the sodium salt, being injected subcutaneously in a volume of 140 cc. The data are summarized in Table I.

The sulfur is excreted slowly. Dakin 6 found similarly that the sulfur excretion after cysteine injection was relatively slow, recovering about 50% of the sulfur of the amino acid in the urine during 36 hours following the injection. In contrast to the results with cysteine the major portion of the methionine sulfur was excreted in the neutral sulfur fraction. The post-injection urines gave a positive reaction with Grote's⁷ test for C-S-S-C compounds. The Sullivan test for cystine, as described by Brand, Harris and Biloon⁸ gave questionable results. The presence of acetone bodies in the urine prevented the interpretation of the usual sodium cyanidesodium nitroprusside test for S-S compounds.