Intracellular pH Measurements In Vivo with a Newly Designed Double-Barrelled Microelectrode and its Application During Skeletal Muscle Ischemia in Rabbits

Abstract

Intracellular pH (pH_ic) is one important regulator of cellular function. It is not known to what extent pH_ic and the buffering capacity are altered during reversible and irreversible ischemic conditions. Already established indirect in vivo techniques such as DMO or CO₂/HCO₃ are not applicable during ischemia, since blood-tissue equilibration of the tracer substances is required. pH determination in tissue homogenates is one possible approach, but it does not allow distinction between intra- and extracellular changes within the tissue. ³¹P NMR has been developed in recent years and this totally non-invasive technique can be used for direct in vivo measurements of pH_ic in skeletal muscle [5]. However, this method requires expensive instruments and, even though separate compartments at different pH give separate peaks in ³¹P NMR spectra, it seems to be difficult to follow changes in the extracellular space in vivo. By the use of pH-sensitive electrodes, on the other hand, it becomes possible to measure in the extracellular as well as in the intracellular compartment.