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, K_m 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.

Modified Kidney Sodium Potassium Adenosine-Triphosphatase Kinetics in Protein Energy Malnutrition

“…In simultaneous studies using an experimental model of this disorder in which rats receiving a protein-deficient diet simulate some of the clinical signs of human kwashiorkor [11], we found similar elevation of kidney microsomal Na,K-ATPase in PEM rats [12]. Na,K-ATPase, an integral membrane protein with vectorial localisation across the membrane, is activated by Na+ from the inner surface of the membrane.…”

“…Group II thus served as the energy-restricted group (ER). The rats were maintained on their respective diets for 7-9 weeks, after which time the PR rats show major symptoms of kwashiorkor [11].…”

Response of Oxidative Phosphorylation in Liver of Protein-Energy Malnourished Rats

“…They were divided into three groups: group 1 (controls), fed 22% casein diet ad libitum; group 2 (energy-restricted), fed 22% casein diet in restricted amounts so as to maintain their body weight similar to group 3 (protein-deficient), which received 1% casein diet ad libitum. The composition o f the diets, maintenance o f animals and experimental protocol were similar to those described earlier (16,17).…”

“…Potter-Elvehjem type homogenizer as described earlier (17). Mitochondrial protein was determined by the modified biuret method in the presence o f deoxycholatc ( 1 1 ).…”

“…Mitochondrial function has, therefore, been studied in a number of hormonal (6, 9), nutritional (7, 10, 19) and other disorders (4,14,15). For some time, we have been interested in examining the nature o f changes consequent to severe dietary restriction of protein and energy in an experimental model (16,17). The present communication deals with the effect o f protein-energy malnutrition on respira tory activity and swelling properties o f mitochondria in such animals.…”