Scaling of Cardiac Oxygen Consumption and Enzyme Activity Levels in Sea Raven (Hemitripterus americanus)

Abstract

Oxygen consumption rate, myoglobin content, and in vitro activities of key enzymes belonging to the major energy-producing pathways have been determined in the myocardia of sea raven (Hemitripterus americanus) spanning a 20-fold size range. Maximal oxygen consumption rate by the isolated, perfused sea raven heart scaled with body size in a direction similar to whole-animal oxygen consumption. The aerobic indicator, cytochrome oxidase, also showed a distribution that was consistent with the accepted metabolism-size scaling paradigm. The activity of lactate dehydrogenase, on the other hand, increased with increasing body size. This finding does not appear to be indicative of an expanded anaerobic potential in the larger hearts, since pyruvate kinase activity scaled in a negative fashion. This was in contrast to data obtained for sea raven white skeletal muscle, where both pyruvate kinase and lactate dehydrogenase activities increased as body size increased.