The Effects of Selective Depletion of Hydrochloric Acid on Acid-Base and Electrolyte Equilibrium *

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Abstract
Dogs were placed on a low Cl diet and depleted of HC1 by twice dally draining their gastric contents and then promptly replacing the Na Cl, KC1, and H2O. Removal of HC1 led to the development of metabolic alka-losis and a small but significant renal loss of K+ and Na+. During the drainage period renal acid excretion was suppressed, but there was a simultaneous rise in extracellular HCO3 concentration, half of which could be accounted for by contraction of the extracellular fluid (ECF). After drainage was discontinued, renal acid excretion increased, and in the new steady state the total rise in HCO3 concentration of 9 mEq/L was more than adequately accounted for by the cumulative negative acid balance; the slight contraction of ECF that existed in the steady state could have explained no more than one-fifth of the increment in HCO3-concentratlon. The persistent elevation of plasma HCO3 concentration indicates that the renal threshold for HCO3 was significantly increased. This finding, taken together with the relatively constant creatlnlne clearance values, provides evidence that the absolute rate of Na+-H+ exchange was accelerated and that this can probably be attributed to a deficiency of reabsorbable anion, i.e., Cl. Administration of Na Cl (and a K-free diet) quickly induced an alkali diuresis and restored normal acid-base balance. In over-all terms the data indicate that removal of Na, K, and H2O during gastric drainage is not a prerequisite to the development of metabolic alkalosis; to the extent that cation and H2O deficits develop, they do so as the result of secondary renal adjustments.