A quantitative approach to acid-base chemistry.

Abstract

In his tribute to the late Dr. Peter Stewart, Dr. Jones outlined the contributions he had made to the field of acid-base regulation. Stewart's approach uses basic physicochemical principles that describe the behaviour of H' in physiological aqueous solutions. These principles are not new; they were used by researchers such as Hastings et al. (1924), Van Slyke et al. (1928), and Henderson et al. (1924) in their investigations of acid-base properties of plasma and whole blood. From the basic physicochemical principles, Stewart constructed a series of equations to quantify the interaction of the three systems governing the behavior of [H'] in physiological aqueous solutions. The purpose of this presentation is twofold: to briefly describe the conventional approach used to describe H' homeostasis during exercise in which lactate (La-) is being produced by glycolysis, and to develop the quantitative physicochemical approach advocated by Stewart to describe H' in physiological aqueous solutions. The information presented here will provide the background needed for an understanding of the underlying principles used in the next series of presentations to quantify the contribution of each system to the [H'] changes occurring in either plasma or muscle during heavy exercise. Intramuscular [H'] ([H'],) increases from 100 nEq . L-' (pH = 7.0) at rest to more than 300 nEq L-' (pH .= 6.5) during maximal exercise which is highly dependent on glycolytic metabolism for a high ATP turnover rate (Spriet et al., 1989). At the same time, arterial plasma [H'] increases from 40 nEq . L-' (pH =: 7.4) at rest to 100 nEq . L-' (pH .= 7.0) (Kowalchuk et al., 1988a; Lindinger and Heigenhauser, 1988). The acidosis in both plasma and muscle during exercise have traditionally been attributed to increased lactic acid concentrations.