Influence of Carbon Dioxide upon Hydrogen Ion Concentration of Frog's Skeletal Muscle

Abstract

The anterior tibial muscles of Rana pipiens were removed, sprinkled with powdered quinhydrone, and mounted between a platinum plate electrode and an agar-KCl bridge connected with a saturated KCl-ealomel half-cell. 1 The muscle and electrodes were inserted in a glass chamber through which known gas mixtures could be flushed. The potential differences were read in the usual way by means of a Type K potentiometer and galvanometer.

After the initial rapid acid shift, muscle macerated with quinhydrone slowly became more and more acid in 5% CO₂ in O₂. Intact muscle in 5% CO₂ in O₂ shifts rapidly acid in the first few minutes' exposure. This reaction is followed by a small alkaline drift, succeeded by a plateau which is maintained for 20 to 40 minutes. The secondary alkaline drift is attributed to the mobilization of base which is presumably a less rapid process than the inward diffusion of CO₂. The plateau usually terminated in an acid drift.

If the plateau values are assumed to be the pH of the tissue at definite CO₂ tensions and if these are compared with the hydrogen ion concentrations calculated from CO₂ combining power data, 2 the agreement is found to be good between 36 and 100 mm. Hg. CO₂ tensions. Above this range the electrometric method gives readings 0.1 to 0.2 pH higher. Below 36 mm. Hg. CO₂ tension, plateau values were not obtained in one hour.

In the presence of tank N₂ or tank O₂ the pH of resting muscle became progressively more acid at a decreasingly rapid rate. Apparently at alkaline reactions (pH 7.3 to 8.0) pure O₂ cannot prevent acid production, although the tissue reaction is maintained at a constant level in the presence of 5% CO₂ in O₂.