Myocardial Oxygen Consumption in the Sea Raven, Hemitripterus Americanus : The Effects of Volume Loading, Pressure Loading and Progressive Hypoxia

Myocardial oxygen consumption was measured using an in situ, perfused heart preparation at 10°C increased in a linear fashion with power output when cardiac output was elevated (volume loading). The increased was possible through improved O2 delivery , but was reduced. The mechanical efficiency of the heart was improved. also increased in a linear fashion with power output when output pressure was increased with constant (pressure loading). The increased was supported by increased O2 removal from the perfusate since oxygen delivery was constant. Once more, improved mechanical efficiency was observed. decreased as O2 delivery was reduced with progressive hypoxia. Even so, power output was maintained at a perfusate input of 81 Torr. Five of 11 hearts survived a 30-Torr exposure, but with a 29 % decrease in power output and a 5-fold reduction in . The increase in the apparent aerobic efficiency which enabled this is discussed.