EFFECT ON BLOOD AND URINE OF INGESTION OF SODIUM BICARBONATE

O·145M NaHCO3 given by stomach tube to conscious dogs caused a fall in plasma solids (protein), decrease in plasma Cl and increase in HCO3; pH of the arterial blood increased but any increase of arterial PCO2, was not significant; plasma K fell. The urine after 0·145M NaHCO3 contained increased amounts of Na with only a small increase in Cl. The increased excretion of Na+ was mainly accompanied by a large excretion of HCO3‐, and the urine became alkaline and contained little NH4+. Changes in the excretion of inorganic PO4, SO4 and K were small. Comparison was made with the effects of the same doses of Na given as 0·122M NaCl+0·023M NaHCO3. This caused an equal fall in plasma solids but no change in plasma Cl, HCO3 and K. The urinary excretion of Na+ increased to rates approximately the same as those produced by NaHCO3 but the main urinary anion was Cl‐, the excretion of which was greatly increased. There was a small excretion of HCO3‐ with larger doses. It is concluded that an important agent determining increased excretion of Na is dilution of the plasma protein, which is common to both types of experiment. The changes in plasma Cl and HCO3 appear to be the factor which determines whether the increased excretion of Na+ is accompanied mainly by HCO3‐ or Cl‐. © 1968 The Physiological Society