THE RELATION OF SULFUR METABOLISM TO ACID-BASE BALANCE AND ELECTROLYTE EXCRETION: THE EFFECTS OF DL-METHIONINE IN NORMAL MAN*†

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Abstract
Balance studies were carried out in normal subjects given 13.9 g of DL-methionine for 5 to 6 days. Administration of methionine produced small reductions in serum CO2 content, associated with acidification of the urine and increased excretion of ammonia. The total cumulative sulfate increment represented approximately 70% of the administered S, and 80 to 85% of the methionine metabolized. During the loading period K excretion increased slightly, but the Na balance did not. With recovery, both Na and K were retained. The changes in acid excretion were related to the reductions in serum CO2 content and the calculated acid retention. Excretion of acid was relatively independent of the urinary sulfate. After final restoration of acid-base balance, accumulated increments in sulfate excretion were virtually equal to the cumulative increments in excretion of "net acid". This strongly suggests the production of 2 equivalents of H+ per mole of oxidized S, and confirms earlier views of the important contribution of S metabolism to the endogenous fixed acid load. Consideration of these data in the light of the known pathways of S metabolism indicates the probable source of the H+ to be cysteine sulfinic acid and acid sulfite.