Effects of Changes in Coronary Blood pH on the Heart

Abstract

The effects of localized acidosis and alkalosis on coronary blood flow, myocardial contractile force, and heart rate were studied in anesthetized, open-chest dogs. Acidosis of the coronary vascular bed was induced by infusion of 5,5-dimethyl-2, 4-oxazolidinedion (DMO) into the total coronary artery inflow, and alkalosis by infusion of tris hydroxymethyl aminomethane (THAM), Na 2 CO 3 or NaHCO 3 . DMO infusion caused an initial slight increase of coronary blood flow, followed by a decrease. The decrease was accompanied by and attributed to a moderate to marked decrease of myocardial contractile force and bradycardia. THAM and Na 2 CO 3 infusion caused a marked increase of coronary blood flow, associated with a decrease of coronary oxygen A-V difference, indicating coronary vasodilation. A slight to moderate increase of myocardial contractile force but little or no change in heart rate was noted. NaHCO 3 infusion caused changes similar to those induced by DMO but of smaller magnitude. It was suggested that the direct effects of DMO and NaHCO 3 are attributable to intracellular acidosis, whereas those of THAM and Na 2 CO 3 are attributable to intracellular alkalosis.