An investigation of the ionic mechanism of intracellular pH regulation in mouse soleus muscle fibres

Abstract

SUMMARY1. Intracellular pH (pH1) of surface fibres of the mouse soleus muscle was measured in vitro by recessed-tip pH-sensitive micro-electrodes. pH1 was displaced in an acid direction by removal of external (NH4)2SO4 after a short exposure, and the mechanism of recovery from this acidification was investigated.2. Removal of external K caused a very slow acidification (probably due to the decreasing Na gradient) but had no effect on the rate of pH, 8. Removal of external C02 or application of SITS (10-4M) caused some slowing of the rate of pH1 recovery following acidification by removal of (NH4)2S04. The effect of SITS was additive to that of Na-free Ringer or amiloride. These results suggest that Cl-HCO3-exchange is also involved in the pH, regulating system and that it is a separate mechanism. Under the conditions used, Cl-HCO3-exchange formed about 20 % of the pH1 regulating system. 9. Decreasing the temperature from 37 to 28 'C not only caused an increase in pHi, but also considerably slowed the rate of pH1 recovery following acidification. We have calculated a Q10 for Na+-H+ exchange of [1][2][3][4] and for Cl-HCO3-exchange, 6-9. 10. We conclude that the pH1 regulating system is comprised of two separate ionic exchange mechanisms. The major mechanism is Na+-H+ exchange, which is probably driven by the transmembrane Na gradient. The other mechanism is Cl-HCO3-exchange, which probably requires metabolic energy.

Astrocytic Acidosis in Hyperglycemic and Complete Ischemia

“…Blood physiological variables were within normal range (Table 1). Muscle pH was 7.02 ± 0.0 1 (range 6.84-7.20), and membrane potential was 75.4 ± 0.4 mY (range 69-83), values consistent with those previously reported for mammalian skeletal muscle (Aickin and Thomas, 1977). Initial pHi measurements were made with ion-selective microelectrodes in which the reference barrel was filled with 150 mM KCI.…”

Ammonium action on post‐synaptic inhibition in crayfish neurones: implications for the mechanism of chloride extrusion

“…First, the i.p.s.p. driving force decreased when the Na+ gradient probably would have both increased on application of NH3/NH4+ (Aickin & Thomas, 1977b) and decreased on application of ouabain or during prolonged exposure to K+-free Ringer solution. Secondly, 50 or 100 % replacement of external Na+ with choline had no obvious effect on the reversal potential of the response to ionophoretically applied GABA (C. C. Aickin & R. A. Deisz; unpublished observations).…”

Extracellular pH, Potassium, and Calcium Activities in Progressive Ischaemia of Rat Cortex

“…There has been little work on the regulation of intracellular pH (pHj) in partial ischaemia, and so it is difficult to predict the pHj at the time when Ke increases dra matically. To speculate, extracellular Na and CI ac tivities are essentially normal and presumably are available for acid-base regulation (Aickin and Thomas, 1977). Thomas (1976) showed that contin uous superfusion with solutions containing high Pco2 caused only a transient decrease in pHj ' Silver (1978) has reported results which suggest that pHj in ischaemia decreases by about 0.1 unit and begins to plateau while pHe continues to decrease.…”