Micro‐electrode measurement of the intracellular pH and buffering power of mouse soleus muscle fibres.

Abstract

SUMMARY1. The intracellular pH (pHi) of surface fibres of the mouse soleus muscle has been measured in vitro using recessed-tip pH-sensitive microelectrodes.2. In 5 % CO2 and pH 7 40, the mean pH1 was 7 07 + 0 007 (s.E. of mean) at 370 C and 7-23 + 0.01 at 280 C. The difference between these two values is the same as the change in neutral pH between 37 and 280 C.3. Alteration of the CO2 level at constant external pH caused a biphasic change in pH1 with a rapid displacement followed by a slower partial recovery. Because the recovery was incomplete, different stable pHi values were recorded at different CO2 levels, the higher the CO2 the lower the pHi. The differences in pHi were highly significant both at 37 and 280 C.4. Alteration of the CO2 level at constant external pH also changed the membrane potential (Em), an increase in CO2 leading to an increased Em. The dependence of Em on the CO2 level was much smaller in the fasttwitch muscle, extensor digitorum longus, than in soleus.5. Changing external pH, either by alteration of the bicarbonate or CO2level of the Ringer solution, caused pHi to change by a mean 38-7 % of the external pH change. The change in pHi was accomplished about 10 times more rapidly, and in the same direction, by altering CO2 than by altering the bicarbonate. 6. Application of external NH3 and NH+ caused a rapid intracellular alkalinization followed by a slower acidification. On removal of external NH3 and NH+, there was a large and rapid acidification, followed by a fairly rapid recovery in pHi.7. The size of the pH1 changes occurring on alteration of the CO2 level at both constant external pH and constant external bicarbonate, and on removal of external NH3 and NH+, suggests a non-CO2 buffering

On the Importance of Acidity in Cancer Cells and Therapy

“…Hagberg et al (1983) [99] measured in vivo the pH i of rabbit skeletal muscle fibers using the double-barreled pH microelectrode. The pH i of 7.00 ± 0.09 found in this study was lower than that found in mouse soleus fibers in vitro using pH-sensitive microelectrodes (7.07) [100] or in rat soleus using double-barreled electrodes (7.1-7.2) [98]. They assumed that the higher bath pH and the lower level of CO 2 in those studies could explain this small discrepancy.…”