Effect of extracellular pH on function and metabolism of isolated perfused rat heart

Abstract

The extracellular pH of the isolated perfused rat heart was varied from 6.9 to 8.0 usually by altering the bicarbonate content of the buffer. Isovolumic left ventricular contractility was measured by an intraventricular balloon. The peak systolic pressure was dependent on the coronary flow rate. At a constant flow rate the peak pressure and cardiac rate were unchanged at 7.4–8.0 but declined at about pH 7.1. The uptake and fate of pyruvate-1-C14 (6 mm) and palmitate-1-C14 (0.7 mm) were similar at pH 7.1–8.0. Compared with pH 7.4, oxidation rates of glucose-U-C14 (5 mm) and acetate-2-C14 (5 mm) were unchanged at pH 7.1, but were greater at pH 8.0. Other increases at pH 8.0 (glucose 5 mm) were in glucose uptake, lactate and pyruvate formation, and the percentage of the glucose uptake accounted for by the sum of C14O2, lactate, and pyruvate formed. It is concluded that in spite of decreased mechanical activity at pH 7.1, Krebs cycle activity is unaltered by pH changes from 7.1 to 8.0, whereas glycolysis and acetate oxidation increase above pH 7.4.