Body Weight, Activities of Cytochrome Oxidase and Electron Transport System in the Liver of the American Plaice Hippoglossoides platessoides. Can these Activities Serve as Indicators of Metabolism?

Abstract

In many organisms, including fish, metabolic rate (oxygen,consumption rate, i/+) is related to body weight (W) allometrically, that is, by a function of the form V a = a W b , boften t a k ~n g a value near 0.8. Metabolic oxidation is controlled by a chain of enzymes and cytochromes known as respiratory electron transport system. This paper tests the hypothesis that the activities of the hepatic electron transport system (ETS) and its terminal oxidase (cytochrome oxidase, CYTOX) are related to W by a similar function for a natural population of American plaice Hippoglossoides platessoides. All measures of hepatic ETS and CYTOX activities (K3 turned out to be significantly related to W by a function of the form K, = cWd, where d = rate of change of enzyme activities with W. The values of dfor the total hepatic ETS and CYTOX activities are 0.90 f 0.03 (S. E,.) and 0.83 f 0.04 (S. E.) respectively. These values are close to 0.8, the value of the exponent for the V.,-W relationship in H. platessoides. The possibility that CYTOX and ETS activities might serve as indicators of routine metabolic rate is discussed in relation to a set of criteria proposed.