Intracellular pH in quiescent and stimulated ventricular myocardium

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Abstract
In ventricular trabeculae from guinea pig and cat heart superfused with a modified Tyrode's solution (pH0=7.4) containing either 137 mM or 103 mM Cl 0 − , intracellular pH (pHi) was measured with H+-sensitive double-barreled microelectrodes. In quiescent preparations pHi was 7.26±0.017 when Cl 0 − was 137 mM, and 7.38±0.02 in 103 mM chloride. In 103 mM Cl 0 − containing saline stimulation of the preparation produced no acidification but in 137 mM Cl 0 − acidification occurred. The acidification was completely revesible when chloride was reduced again. When HCO 3 − /Cl− exchange was blocked by 0.5 mM SITS, pHi was lowered similar to the effect of increasing extracellular chloride concentration. It was concluded that when Cl 0 − is raised, the HCO 3 − /Cl− exchanger operates as a Cl−/Cl− exchanger.