Function and energy metabolism of the isolated heart as influenced by variation in pH, P CO2 , and HCO 3 . II. Concentrations of phosphate metabolites

Abstract

Effects of variation of pH (7.0–7.9) on myocardial concentrations of high energy phosphate, creatine and inorganic phosphate were investigated in isolated guina pig hearts over a period of 2 h. Remarkable changes were observed in the myocardial concentration of inorganic phosphate and in the mass action ratio of the creatine kinase. The myocardial concentration of inorganic phosphate is generally elevated up to 140% at higher, and reduced at lower pH-values. The mass action ratio of the creatine kinase increases up to 200% at pH 7.9 with a time lag of 1 h and decreases at pH 7.0. The changes in the mass action ratio are much smaller than those, which can be calculated from the creatine kinase equilibrium, especially with respect to participation of H+-ions. Intracellular compartmentalisation of metabolites and flow equilibrium involving two isoenzymes of creatine kinase at different cellular sites are discussed as possible explanations of the discrepancies between the observed and calculated mass action ratio.