Brain pH responses to sodium bicarbonate and Carbicarb during systemic acidosis

Rats subjected to ammonium chloride-induced metabolic acidosis or respiratory acidosis caused by hypercapnia were given alkalinization therapy with either sodium bicarbonate or Carbicarb. Ammonium chloride induced dose-dependent systemic acidosis but did not affect intracellular brain pH. Hypercapnia caused dose-dependent systemic acidosis as well as decreases in intracellular brain pH. Sodium bicarbonate treatment resulted in systemic alkalinization and increases in arterial PCO2 in both acidosis models, but it caused intracellular brain acidification in rats with ammonium chloride acidosis. Carbicarb therapy resulted in systemic alkalinization without major changes in arterial PCO2 and intracellular brain alkalinization in both acidosis models. These data demonstrate that bicarbonate therapy of systemic acidosis may be associated with "paradoxical" intracellular brain acidosis, whereas Carbicarb causes both systemic and intracellular alkalinization under conditions of fixed ventilation.