THE DISPOSITION OF ACID ADMINISTERED TO SODIUM-DEPLETED SUBJECTS: THE RENAL RESPONSE AND THE ROLE OF THE WHOLE BODY BUFFERS 12

Abstract

Na depletion modified the usual renal response of normal human subjects to acidifying salts in several respects: (1) ammonium excretion was relatively greater and more prompt; (2) there was no Na diuresis with urine anion loads less than 125 m.eq., and Na constituted only a small, fixed proportion of all cation excreted in excess of this amt.; (3) initial excretion of K was increased. During the period of acid admn. most of the H2 was distr. among the body buffers with the kidneys playing a secondary role. The largest moiety of the retained H2 was buffered in tissue or bone, where it mainly exchanged for K. Whole blood buffers received less than a fifth of the retained acid. The initial renal ammonium response was directly proportional to rate of excretion of the loading anion and was not related to the degree of extracellular acidosis or to urine pH. In the postacidification period ammonium excretion exceeded the excretion of loading anion by an amt. nearly equal to the simultaneous retention of K, thus permitting the delivery of H2 from intracellular fluid in exchange for K. These data are consistent with the hypothesis that the stimulus for ammonium excretion was increased tubular reabsorption of fixed cation in the presence of obligatory anion excretion.