Tissue Cytochrome Oxidase Activity and Copper, Iron, and Pantothenic Acid Nutrition in the Growing Rat

Abstract

Relative effects of graded dietary levels and combinations of copper, iron, and pantothenic acid on liver, brain, and bone ossification center cytochrome oxidase activities were investigated in growing rats. Dietary iron and copper but not pantothenic acid have been shown to influence tissue levels of cytochrome oxidase. Three experiments using 124 rats with a low copper (1 ppm), low iron (10 ppm) skim milk diet were carried out. In experiments 1, 2, and 3, the basal diet was supplemented with cupric chloride and ferric oxide to give 1, 10, 30, 122, and 501 ppm copper, 60 ppm iron, and 33 ppm pantothenic acid (8 weeks duration); 1, 10, and 30 ppm copper, 10 ppm iron, and 33 and 120 ppm pantothenic acid (6 weeks); and 1, 10, and 30 ppm copper, and 19, 60, and 214 ppm iron with 66 ppm pantothenic acid (4 weeks), respectively. In addition, half of the eight replicates in the first two experiments were injected with 280 µg iron twice per week. Graded levels of dietary copper resulted in positive linear and/or quadratic responses in liver, brain, and tibia ossification center cytochrome oxidase activities and also in liver copper. The decrease in liver copper with added pantothenic acid was paralleled by an increase in the liver and tibia cytochrome oxidase activities at 30 ppm copper. When dietary copper was increased from 10 to 30 ppm, a decrease in liver cytochrome oxidase activity was found with 33 ppm but not with 66 or 120 ppm pantothenic acid. The data indicated that at higher levels of copper, there was an increase in the requirement for pantothenic acid. Additional iron either injected or via the diet increased liver cytochrome oxidase activity in the anemic rat. However, in the nonanemic rat, additional iron that produced an iron overload decreased liver cytochrome oxidase activity. Data from the three experiments indicated that available copper for cytochrome oxidase activity is affected in decreasing magnitude by dietary copper, pantothenic acid, copper-pantothenic acid interaction, and iron.