Pflügers Archiv

, Volume 349, Issue 4, pp 285–294 | Cite as

Intracellular bicarbonate in single skeletal muscle fibers

  • R. N. Khuri
  • K. K. Bogharian
  • S. K. Agulian
Article

Summary

This is the first direct potentiometric determination of intracellular bicarbonate concentration. The new method involves the use of a double-barrelled HCO3-selective liquid ion-exchange microelectrode that permits the simultaneous determination of intracellular [HCO3] and membrane PD of single cells. The mean in situ intracellular [HCO3] of single striated muscle fibers was 4.4±0.3 mM/l in the frog and 12.6±0.6 mM in the rat. Both values are inconsistent with a Donnan equilibrium distribution and can be accounted for by an active HCO3 influx or an active H+ efflux. During progressive acute hypercapnia there is an accumulative build-up of intracellular bicarbonate in rat skeletal muscle. The increase in intracellular [HCO3] with hypercapnia is strictly proportional to the associated increase in plasma [HCO3], thus maintaining a constant ratio of extracellular: intracellular [HCO3]. Using the directly measured [HCO3] in cell water, we calculate a cell pH of 7.00 for frog fibers and of 7.14 for rat fibers, both values being about 1.1 pH units on the alkaline side of those predicted for a Donnan equilibrium distribution of H+ ions across the cell membrane.

Key words

Bicarbonate Microelectrode Intracellular Bicarbonate Cell Bicarbonate Muscle Cell Bicarbonate Cell pH 

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Copyright information

© Springer-Verlag 1974

Authors and Affiliations

  • R. N. Khuri
    • 1
  • K. K. Bogharian
    • 1
  • S. K. Agulian
    • 1
  1. 1.Department of PhysiologyAmerican University of BeirutBeirutLebanon

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