The intracellular pH was determined from the cardiac muscles in rabbits from 12 normal, 12 acute metabolic acidosis and 9 acute metabolic alkalosis, using 5, 5-dimethyi-2, 4-oxazolidinedione (DMO) method.
Metabolic acidosis was produced by intravenous infusion of hydrochloric acid and metabolic alkalosis by sodium bicarbonate solution.
The relationship between intracellular and extracellular hydrogen ion concentrations and electrocardiographic patterns were also studied and discussed.
1) In normal rabbits, acid-base parameters of blood were pH 7.44, hydrogen ion concentration 36 nM /L, Pcoz 28 mmHg, bicarbonate ion concentration 18.9 mEq/L and those of the cardiac muscles were pH 6.98, hydrogen ion concentration 104 nM/L., and bicarbonate ion concentration 9.0 mEq/L respectively.
2) By the induction of acute extracellular acidosis with intravenous infusion of 11 m117 ml/kg of hydrochloric acid (300 mEq/L), blood pH decreased from 7.48 to 7.02 and cardiac muscle pH from 6.98 to 6.87. On the contrary, by the acute extracellular alkalosis with intravenous infusion of 12 m120 ml/kg of sodium bicarbonate (600 mEq/L), blood pH increased from 7.44 to 7.58, and cardiac muscle pH from 6.98 to 7.06.
3) Hydrogen ion concentration ratio (Hi/He) between blood and cardiac muscle was 2.9 in normal, whereas it was 1.6 in metabolic acidosis and 3.4 in metabolic alkalosis. The relationship between hydrogen ion concentration of blood and cardiac muscle could be expressed in an equation of (H+)i=76.0 +0.67 (H+)e.
4) It seemed that the electrocardiographic patterns in acute metabolic acidosis and alkalosis were mainly correlated with the increase or decrease in plasma concentration of potassium which was exchanged for intracellular hydrogen ion rather than hydrogen ion itself.
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