[Measurement of intracellular bicarbonate and pH: preliminary study using potentiometric determination of muscle acid-labile CO2].

A method is described for the determination of total acid-labile CO2 (TCO2) and intracellular bicarbonate concentration [HCO3-] in skeletal muscle samples. Surgical biopsies obtained from the quadriceps femoris muscle of 24 Wistar male rats were analyzed for acid-labile CO2 and extra and intracellular water, extracellular water was estimated from the muscle chloride content. TCO2 method utilizes a single diffusion step with absorption of extracted CO2 by sulphuric acid into barium hydroxide and subsequent potentiometric determination of muscle CO2 content. The measured total CO2 content in muscle was 12.01 +/- 1.06 mMol/Kg wet weight when the sample weight was kept in terms of 22-110 mg, assuming a normal membrane potential and a muscle pCO2 equal to femoral vein blood pCO2, calculated intracellular bicarbonate concentration was 12.58 +/- 1.08 mEq/1 H2O i.c. (X +/- D.S.) and intracellular pH was 7.03 +/- 0.04 (X +/- D.S.).