The Effect of H+— and Lactate Ions on the Electrical Activity and Content of High Energy Phosphate Compounds of Taenia Coli from the Guinea Pig

Reduction of the pH in Krebs solution with 0.05–0.4 units by adding lactic acid or acetic acid to a final concentration of 0.1–1.0 mmoles/l or by increasing the CO2 concentration from 3–12 % (pH change 0.28) in the gassing mixture caused relaxation of isolated taenia coli from the guinea pig. In determining the electrical activity of the membrane of the muscle by the “sucrose gap” method, it was found that a pH reduction inhibited the action potential, and with yet lower pH values hyperpolarization was observed. In K+‐depolarized muscle a similar pH reduction had a tension‐increasing effect. Na+‐lactate increased the electrical activity of the membrane and had a tension‐increasing effect. — The addition of lactic acid in a concentration of 1 mmole/l which relaxed the carbacholine stimulated muscle, had no effect on the content of high energy phosphate compounds. It seems probable that the relaxing effect of H+‐ions was a result of its inhibitory effect on the electrical activity of the membrane.