Oxygen Consumption, Carbon Dioxide Production and Enzyme Activities of Isolated Working Octopus Heart

Abstract

The heart of Octopus vulgaris (Lam.) presents an ideal tissue for in vitro studies. Its performance, when perfused with haemocyanin solutions or blood, closely matches that in vivo in terms of power output (Agnisola and Houlihan, 1991) and the heart tissue is self-perfused so that with each contraction a proportion of the fluid in the lumen passes through the heart wall in a system of blood vessels to produce coronary flow (Houlihan et al. 1987). Comparison of in vitro activity levels of key enzymes from energy-generating pathways (Driedzic et al. 1990) with rates of oxygen consumption of perfused hearts, working at subphysiological levels (Houlihan et al. 1987) suggested that the tissue is fuelled primarily by a glucose-based metabolism. In this experiment, the analysis is refined with the simultaneous measurement of oxygen consumption, carbon dioxide production and enzyme activity levels on the same tissues. Hexokinase activity was determined since it is a good indicator of maximal aerobic glucose use in a variety of muscles (Crabtree and Newsholme, 1972), citrate synthase and cytochrome oxidase activities were measured as markers of aerobic capacity, and 3-hydroxyacyl CoA dehydrogenase activity was assayed as a qualitative index of the capacity to oxidize fatty-acid-derived fuels.