The Mechanochemistry of Cardiac Muscle

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Abstract
The utilization of creatine phosphate (CP) andadenosine triphosphate (ATP) was studied in the iodoacetate (IAA) and nitrogen (N2)-treated cat papillary muscle. Under these conditions the net production of ATP is reflected in a fall in CP concentration. The rate of energy utilization of the IAA-N2-treated cat papillary muscle resting without tension was 0.68 [mu]mole CP/g/min. This rate was increased to 1.07 [mu]mole/g/min when muscles were passively stretched with 2 g of tension. In a series of isometrically contracting muscles CP utilization was found to be proportional to the number of activations and the summated contractile element work. These rates of CP utilization were 0.083 [mu]mole/g/activation and 0.0059 [mu]mole/g-cm of work. The calculated mechanochemical coupling efficiency was 33%.