Metabolism and acid-base physiology.

The purpose of this paper is to review the pathways of hydrogen ion production and removal due to intermediary metabolism. The principal method of analysis employed was one based on a theoretical approach because it is the most accurate and has the broadest application. In the absence of hypoxia and insulin deficiency, carbohydrates and neutral lipids will not make significant contributions to acid-base balance. During normal metabolism, the oxidation of proteins leads to an acid load. The majority of protons are produced from the oxidation of cationic plus sulfur-containing amino acids, whereas they are removed when anionic amino acids are oxidized. Organic anions, if they can be metabolized in vivo, lead to an equivalent degree of proton removal. Small contributions to acid-base metabolism are made by phospholipid and purine oxidations. Special reactions involving calcium contribute to the acid load in that the precipitation of calcium carbonate or phosphate in bone or in the gastrointestinal tract will result in proton liberation. When all of the above are considered, the clinician can make a reasonably accurate estimate of the rate of acid production.