Cardiac performance as a function of intracellular oxygen tension in buffer-perfused hearts.
Critical intracellular myocardial oxygen tension was determined by optical spectroscopic measurement of myoglobin oxygen saturation in crystalloid-perfused guinea pig hearts. Accurate end-point determinations of the maximally oxygenated and deoxygenated myoglobin were made. Hearts were subjected to a steady decrease in perfusate oxygen tension while left ventricular developed pressure, maximal left ventricular dP/dt, myocardial oxygen consumption, lactate release, and adenosine release were measured as indices of myocardial function. Intracellular myoglobin was found to be only 72% saturated under baseline conditions with an arterial oxygen tension of >600 mmHg at 37 degrees C. Baseline intracellular oxygen tension was 6.3 mmHg. Myocardial oxygen consumption was decreased by 10% when the oxygen tension fell to 5.7 mmHg, and cardiac contraction decreased 10% when oxygen tension was 4.1 mmHg. Adenosine release and, finally, lactate release began to increase at sequentially lower oxygen tensions. The present results indicate that the buffer-perfused guinea pig heart at 37 degrees C has an intracellular oxygen tension just above the threshold for impaired function.
Schenkman
K A
KA
Department of Pediatrics, University of Washington, Seattle, 98195, USA. kschen@chmc.org
D000241:Adenosine / Q000096:biosynthesis; D000818:Animals; D002021:Buffers; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000096:biosynthesis; D008297:Male; D009206:Myocardium / Q000378:metabolism; D009211:Myoglobin / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D010477:Perfusion; D013057:Spectrum Analysis / Q000379:methods; D016277:Ventricular Function, Left / Q000502:physiology*; D017725:Ventricular Pressure / Q000502:physiology
D002021:Buffers; D009211:Myoglobin; D019344:Lactic Acid; D000241:Adenosine; D010100:Oxygen