Effect of furosemide on collecting-duct hydrogen ion secretion in the rabbit

The purpose of this study was to determine the effect of acute furosemide administration on urine acidification. U-B Pco2 was used to assess collecting-duct hydrogen ion secretion in rabbits infused with bicarbonate. Prior to furosemide administration, the U-B Pco2 was virtually zero, indicating very low or absent hydrogen ion secretion in the collecting duct. Intravenous furosemide infusion resulted in a significant increase in the U-B Pco2. This increase could not be attributed to changes in blood Pco2, plasma potassium concentration, or urine phosphate concentration and buffer capacity. Furthermore, the rise in U-B Pco2 was independent of any change in urine bicarbonate concentration. We conclude that furosemide leads to an augmentation of collecting-duct hydrogen ion secretion in the rabbit, perhaps by increasing sodium reabsorption in the collecting duct.