THREE-STEP-REGULATION OF ACID-BASE BALANCE IN BODY FLUID AFTER ACID LOAD

Twenty five mongrel adult dogs were infused with isotonic HC1 solution (0.6-9.2 mEq/Kg), and the changes of acid-base balance in the blood and the excretion of excessive acid in the urine were observed until the normal acid-base balance in body fluid was restored. Results obtained are outlined as follows: 1. The pH and bicarbonate in the blood decreased in proportion to the acid load at the end of acid infusion, and depression of pH and bicarbonate in the blood of 3 dogs out of 5 which died of the acidosis was over 0.2 pH and 15 mEq/l respectively.2. The acid infused was neutralized mainly (about 60%) by the extracellular buffer (especially by bicarbonate), and the rest (about 40%) by the intracellular buffer at the end of infusion. After 24 hours, however, the large part of acid load (about 3/4 of the total) was buffered by the intracellular fluid, a part (1/4) was excreted in urine, and thus the alkali reserve in extracellular fluid was completely restored. The excess acid was gradually excreted after a lapse of days mainly as ammonium chloride and partly titratable acid, or inclusively as the base economy. After 2-8 days, the excretion was completed.Thus the regulation of acid-base balance in body fluid after acid loading was carried out in three steps, i. e. neutralization by extracellular buffer, neutralization by intracellular buffer and renal excretion as the base economy.3. By measuring the distribution and the amounts of Na, K, Cl and HCO3 in extracellular fluid, it was confirmed that neutralization by intracellular buffer after acid administration was effected mainly by an alkali shift from the cells in the early period, and by the penetration of the acid radical (Cl) into the cells thereafter.