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

J Physiol. 1986 Dec;381:241-61. doi: 10.1113/jphysiol.1986.sp016325.

Abstract

1. 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 pHi was 7.40-7.50. This range was too high to be explained by a passive distribution of H+, OH- or HCO3-. 4. In nominally HCO3(-)-free, HEPES-buffered solution, cells were acid loaded by addition and subsequent withdrawal of NH4+ from the superfusate. pHi 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 pHo. 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 Cl-. 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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
  • 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / analogs & derivatives
  • 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / pharmacology
  • Adult
  • Amiloride / pharmacology
  • Ammonium Chloride / pharmacology
  • Animals
  • Bicarbonates / pharmacology
  • Brain / physiology*
  • Chlorides / pharmacology
  • Fishes / physiology*
  • HEPES / pharmacology
  • Homeostasis / drug effects*
  • Humans
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Lampreys / physiology*
  • Neurons / physiology*
  • Prohibitins
  • Sodium / pharmacology
  • Spinal Cord / physiology*

Substances

  • Bicarbonates
  • Chlorides
  • PHB protein, human
  • Prohibitins
  • Ammonium Chloride
  • 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid
  • Amiloride
  • Sodium
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
  • HEPES