RELATIONSHIP BETWEEN INTRACELLULAR CALCIUM AND OXYGEN-CONSUMPTION - EFFECTS OF PERFUSION-PRESSURE, EXTRACELLULAR CALCIUM, DOBUTAMINE, AND NIFEDIPINE

All of the mechanisms that connect the cardiac mechanical work load wi th energy production have not been clearly defined. The purpose of thi s study was to evaluate the relationship between intracellular calcium and oxygen consumption in intact hearts, to further understand this r elationship. Intracellular calcium was measured in isolated nonworking perfused rat hearts loaded with Indo-1 by means of a surface fluorome try technique. Glucose was used as a substrate. Myocardial contraction and oxygen consumption were modulated by perfusion pressure (80, 110, and 140 cm of water), extracellular calcium (1, 2, 3, and 4 mmol/L), dobutamine (10(-6) mol/L), and nifedipine (10(-6) mol/L). With all of these interventions there was a close correlation between intracellula r calcium (systolic, diastolic, and amplitude) and oxygen consumption or left ventricular developed pressure. Observations in this study sup port the hypothesis that intracellular calcium plays a regulatory role in the link between cardiac mechanics and energy production.