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

Abstract

SUMMARY1. The regulation of intracellular pH (pHi) in lamprey reticulospinal neurones was investigated with pH-sensitive micro-electrodes based on a neutral carrier liquid membrane. Experiments were performed using an in vitro brain-stem preparation.2. In HEPES-buffered solutions, extracellular pH (pHO) was consistently more acidic than the pH of the bathing solution (pHb). In HCO3--buffered solutions, the brain was also relatively acidic, but the brain pH gradient was smaller.3. In HEPES-and HCO3--buffered solutions, mean pH, was 7 40-7 50. This range was too high to be explained by a passive distribution of H+, OH-or HC03-.4. In nominally HC03--free, HEPES-buffered solution, cells were acid loaded by addition and subsequent withdrawal of NH4+ from the superfusate. pH1 recovered from acid loading by an energy-dependent process in 10-20 min. Recovery from acid loading in HEPES-buffered solutions was blocked by exposure to amiloride.5. Removal of extracellular Na+ caused a slow, accelerating fall of pHi. Return of Na+ to the bath caused an immediate reversal of this acidification, followed by a slow recovery of pHi. Measurement with Na+-sensitive micro-electrodes during acid loading showed a rapid rise in the intracellular Na+ activity ([Na+]i).6. Following acid loading, transition from HEPES-to HCO3--buffered solutions caused an increase in the acid extrusion rate of at least 48 %. The effect of these solution changes was dependent on pH0. After blocking pHi recovery with amiloride, transition from HEPES-to HCO3--buffered Ringer plus amiloride produced a slow recovery of pHi.7. Recovery from acid loading in HCO3--buffered solutions was inhibited 65 % by the anion transport blocker DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid). Recovery from acid loading after incubation in Cl--free solution was slower than recovery after replenishment of C1-.8. It is concluded that in HCO3--free solutions, pHi regulation is accomplished by a Na-H exchange mechanism. In the presence of extracellular HCO3-an additional mechanism can operate to extrude intracellular acid.

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

“…Previous investigators had used extracellular electrodes to monitor transient changes in pH caused by the addition of CO 2 /HCO 3 Ϫ to the fluid surrounding skeletal muscle fibers (31) or lamprey neurons (15). We have adapted their approach to track pH S as CO 2 crosses the cell membrane of Xenopus oocytes.…”

“…In his experiments on lamprey neurons, Chesler (15) found that applying CO 2 / HCO 3 Ϫ did not cause a transient increase in pH S , but a decrease. Importantly, these neurons, unlike the oocytes in our experiments, had a powerful transport mechanism for the uptake of HCO 3 Ϫ (or an equivalent species, such as COញ 3 ).…”

Regulation of Intracellular pH in Single Rat Cortical Neurons in vitro: A Microspectrofluorometric Study

“…Although different type of neurons have been the subject of subsequent stud ies (Chesler, 1990), there have been comparatively few reports of pH regulation in vertebrate neurons. Some authors have concluded that an Na + IH+ ex changer is solely responsible for acid extrusion in vertebrate neurons (Nachsen and Drapeau, 1988;Gaillard and Dupont, 1990), while others have found evidence for additional HC03 --dependent acid extrusion mechanisms (Chesler, 1986;Pocock and Richards, 1989;Raley-Susman et aI., 1991). There are no previous studies of pH regulation in vertebrate neurons following alkaline transients or concerning the effect of pHe on pHi-regulating mechanisms.…”

Ionic control of intracellular pH in rat cerebellar Purkinje cells maintained in culture.

“…Thus, to understand the relationships between pHi and electrical properties of nerve cells, it is necessary to determine the mechanisms involved in pHi regulation of these cells. While these mechanisms have been well documented in a great variety of non-mammalian nerve cells (Thomas, 1977; Moody, 1981;Schlue & Thomas, 1985;Chesler, 1986;Deitmer & Schlue, 1987), little is known about mammalian CNS cells. Nevertheless, considerable results have already been reported concerning the membrane properties of many mammalian CNS neurones.…”