The influence of muscle respiration and glycolysis on surface and intracellular pH in fibres of the rat soleus.

Abstract

SUMMARY1. Extracellular pH (pH.) and intracellular pH (pHi) of superficial fibres of the rat soleus muscle were measured in vitro using pH-sensitive glass micro-electrodes. The origin of the pH gradient existing between the bulk--phaseofextracellular solution and the surface of muscle fibres was investigated.2. The pHo decreased almost linearly over a distance of 285 ,um from bulk solution to fibre surface. The magnitude of the bulk-surface pH gradient is greater in the mid region of the muscle than close to the tendon.3. Decreasing the superfusate velocity increased the magnitude of the pH gradient. Reducing the buffer capacity of the superfusing solution had the same effect.4. Inhibiting the aerobic metabolism or stimulating it acidified the fibre surface. Inhibiting glycolysis alone, or both aerobic metabolism and glycolysis, alkalinized the fibre surface.5. Inhibiting the membrane ionic exchange process involved in pHi regulation had no effect on surface pH.6. Changing the rate of aerobic or anaerobic metabolism quickly modified pHi in most cases.7. In conclusion the bulk-surface pH gradient seems to result mainly from diffusion of CO2 and lactic acid across an unstirred layer of fluid covering the surface of muscle fibres.

Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase II enhances CO2 fluxes across Xenopus oocyte plasma membranes

“…The upper records in Fig. 2, A and B, show that applying of CO 2 /HCO 3 Ϫ causes a transient rise in pH S , as previously reported (22,31). We define the maximal pH S change as ⌬pH S ; it is positive for CO 2 influx and negative for CO 2 efflux.…”

“…The depleted CO 2 at the cell surface is replenished by 1) diffusion from the BECF and 2) the reaction HCO 3 Ϫ ϩ H ϩ ¡ CO 2 ϩ H 2 O at the cell surface. Because this reaction consumes H ϩ , pH S rises, as observed by De Hemptinne and Huguenin (31) and by Saarikoski and Kaila (59). The reaction also depletes HCO 3 Ϫ at the cell surface, and we would expect that the diffusion of H ϩ and HCO 3 Ϫ from the BECF would replenish the depleted H ϩ and HCO 3 Ϫ at the cell surface.…”

Regulation of intracellular pH in reticulospinal neurones of the lamprey, Petromyzon marinus.

“…Since pH. may be less than the pH of the bathing solution (Kraig et al 1983;De Hemptinne & Huguenin, 1984) (Fig. 1 A).…”

Relative CO2/NH3 selectivities of mammalian aquaporins 0–9

“…As an extension to the aforementioned pH i methodology for assessing the relative permeabilities of a cell membrane to dissolved gases, our laboratory exploited a principle revealed by earlier work in which investigators had monitored surface pH (pH S ) or tissue extracellular pH (pH o ) while exposing cells to CO 2 /HCO 3 Ϫ (11,57) or NH 3 /NH 4 ϩ (8). The novelty of our approach was to push a relatively large pH-sensitive microelectrode up against the surface of an oocyte and to use transient changes in pH S to assess the membrane permeability of gases that alter pH (i.e., CO 2 and NH 3 ).…”