Rat Liver Mitochondrial Cytochrome c Oxidase and Cytochromes in Experimental Protein-Energy Malnutrition

Abstract

Cytochrome c oxidase activity and cytochromes b, (c+c1) and a(+a3) concentrations were determined in liver mitochondria from rats fed the following diets: controls (group 1) fed ad libitum, energy-restricted (group 2) and protein-deficient (group 3). The animals were fed for two time intervals, 3--5 and 7--9 weeks. At 3--5 weeks, the cytochrome oxidase specific activity (nmol cytochrome c oxidized/mg protein/min) and cytochrome concentrations (nmol/mg protein) were not different in groups 2 and 3 as compared to group 1. At 7--9 weeks, the cytochrome oxidase specific activity and concentrations of cytochromes b, (c+c1) and a(+a3) were significantly reduced in group 2 rats as compared to well-fed controls. The Michaelis-Menten constant, Km apparent for ferrocytochrome c, was significantly higher in group 2 as compared to group 1. In group 3 rats, cytochrome oxidase specific activity and cytochrome b, a(+a3) concentrations were not different from group 1 at 7-9 weeks. However, cytochrome (c+c1) concentration was higher in group 3, resulting in an elevated ratio of cytochrome (c+c1) to cytochrome a(+a3) as compared to groups 1 and 2.