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Matching of cardiac oxygen delivery and fuel supply to energy demand in teleosts and cephalopods

1988; NRC Research Press; Volume: 66; Issue: 5 Linguagem: Inglês

10.1139/z88-158

1480-3283

William R. Driedzic,

Marine Bivalve and Aquaculture Studies

Both fish and cephalopods have a single systemic ventricle which performs mechanical work at similar levels in the two groups of organisms. This example of convergent evolution is used to identify common features of cardiac oxygen delivery and fuel supply in relation to energy demand. Foremost, both groups of animals exhibit morphological alterations to enhance oxygen delivery to the myocardium. In cephalopods, the heart is positioned to directly receive oxygenated blood, and coronary arteries can be present in both fish and cephalopods. At the cellular level, oxygen extraction is facilitated by elevated concentrations of myoglobin in the hearts of fish, which face particularly acute low levels of extracellular oxygen. These features represent adaptations to meet the challenge of oxygen delivery. In temperate-zone teleosts and cephalopods, maximal in vitro activity of ATPase reflects maximal in situ oxygen demand. In both groups of animals, there is a linear relationship between maximal in vitro hexokinase and ATPase activities, and in temperate-zone teleosts a similar relationship exists between carnitine palmitoyl transferase and ATPase activities. These enzyme activities are interpreted to reflect adaptations in maximal capacities to utilize glucose and fatty acids in response to increased energy demand.