Intracellular pH and Bicarbonate Concentration as Determined in Biopsy Samples from the Quadriceps Muscle of Man at Rest

Abstract

A method for measuring intracellular pH and bicarbonate concentration of human muscle is described. Muscle biopsies from the quadriceps muscle of 13 healthy subjects at rest were analyzed for acid-labile CO2 and volume of extra- and intra-cellular water. Extracellular water volume was estimated from the chloride content and intracellular water volume from the K content, or alternatively derived from the sample weight. Measured total CO2 content in muscle was 9.84 .+-. 1.39 mmol/kg. Assuming a normal membrane potential (88 mV) and PCO2 [CO2 tension] of muscle equal to venous blood, calculated intracellular pH was 7.00 .+-. 0.06 and intracellular bicarbonate concentration was 10.2 .+-. 1.2 mmol/l of water.