The role of bicarbonate, chloride and sodium ions in the regulation of intracellular pH in snail neurones.
1. Intracellular pH (pH(i)), Cl(-) and Na(+) levels were recorded in snail neurones using ion-sensitive micro-electrodes, and the mechanism of the pH(i) recovery from internal acidification investigated.2. Reducing the external HCO(3) (-) concentration greatly inhibited the rate of pH(i) recovery from HCl injection.3. Reducing external Cl(-) did not inhibit pH(i) recovery, but reducing internal Cl(-), by exposing the cell to sulphate Ringer, inhibited pH(i) recovery from CO(2) application.4. During pH(i) recovery from CO(2) application the internal Cl(-) concentration decreased. The measured fall in internal Cl(-) concentration averaged about 25% of the calculated increase in internal HCO(3) (-).5. Removal of external Na inhibited the pH(i) recovery from either CO(2) application or HCl injection.6. During the pH(i) recovery from acidification there was an increase in the internal Na(+) concentration ([Na(+)](i)). The increase was larger than that occurring when the Na pump was inhibited by K-free Ringer.7. The increase in [Na(+)](i) that occurred during pH(i) recovery from an injection of HCl was about half of that produced by a similar injection of NaCl.8. The inhibitory effects of Na-free Ringer and of the anion exchange inhibitor SITS on pH(i) recovery after HCl injection were not additive.9. It is concluded that the pH(i) regulating system involves tightly linked Cl(-)-HCO(3) (-) and Na(+)-H(+) exchange, with Na entry down its concentration gradient probably providing the energy to drive the movement inwards of HCO(3) (-) and the movement outward of Cl(-) and H(+) ions.
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism* / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism* / Q000494:pharmacology; D006851:Hydrochloric Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D012908:Snails / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology
D001639:Bicarbonates; D002712:Chlorides; D012965:Sodium Chloride; D012964:Sodium; D006851:Hydrochloric Acid