1. Urinary sodium and hydrogen ion excretion was measured in four normal subjects before and after they had ingested 25 g of glucose. The subjects were studied during a sustained water diuresis after an overnight fast and after a 40 h fast.
2. After glucose had been ingested, urinary sodium excretion was reduced by approximately 40% but there was no change in urine flow. The decrease in sodium excretion was associated with a rise in hydrogen ion excretion.
3. These results suggest that sodium ion is retained in exchange for hydrogen ion in the distal segment of the nephron.
4. It is postulated that the increased renal bicarbonate threshold and the metabolic alkalosis which develop when glucose is given to fasted subjects are a consequence of this exchange.