ANTIOXIDANT ENZYME-ACTIVITY IN THE MUSCLES OF CALVES DEPLETED OF VITAMIN-E OR SELENIUM OR BOTH

Feeding diets depleted of vitamin E and Se to cattle can induce a dise ase known as nutritional degenerative myopathy. It is believed that an increased peroxidative challenge in muscle is involved in the pathoge nesis of this disease. A number of species can up-regulate the activit y of some antioxidant enzymes, including glutathione reductase (EC 1.6 .4.2), glutathione transferase (EC 2.5.1.18), glucose-6-phosphate dehy drogenase (EC 1.1.1.49), catalase (EC 1.11.1.6), and superoxide dismut ase (EC 1.15.1.1), in an attempt to mitigate the effects of a peroxida tive challenge. A 2 x 2 factorial study was set up to examine possible changes in the activities of these antioxidant enzymes in muscles of ruminant calves fed on diets lon in either vitamin E or Se. Four group s of four calves each were fed on a basal diet of NaOH-treated barley which was supplemented with alpha-tocopherol or Se or both for a total of 50 weeks. Calves fed on diets depleted of vitamin E, but not those fed on diets low in Se, developed subclinical myopathy, as judged by increases in the activity of plasma creatine kinase (EC 2.7.3.2), and had increased muscle concentrations of two indices of lipid peroxidati on, namely thiobarbituric acid-reactive substances, with and without a scorbate activation. Feeding diets depleted of vitamin E and diets low in Se both increased muscle activities of glucose-6-phosphate dehydro genase in heart, biceps and supraspinatus. This change may have occurr ed in an attempt to maintain intracellular pools of reduced glutathion e. No other changes in antioxidant enzyme activity were observed.