Influence of dietary selenium supplementation and exercise on thiol-containing enzymes in mice

Exercise markedly increases oxygen uptake by active muscles and consequently increases generation of reactive oxygen species. A dietary deficiency in selenium (Se) can increase the sensitivity of the living system to oxidative stress. delta-Aminolevulinate dehydratase (delta-ALA-D), succinate dehydrogenase (SDH), and lactate dehydrogenase (LDH) are sulfhydryl-containing enzymes, and their activities are sensitive to the presence of oxidizing agents. We investigated the effect of Se deficiency and supplementation on delta-ALA-D, SDH, and LDH activities in mice subjected to swim training for 8 wk.

Three-month-old female mice were randomly assigned and fed a basal diet, a basal diet plus 1 ppm of Se, and a basal diet plus 40 ppm of Se. These groups were further divided into sedentary and swim-trained groups. A mass equivalent of 5% of the animal's body weight was fixed to the tail. Animals were then exercised for 60 min/d, 4 d/wk.

Swim-training associated with Se-deficient diet diminished delta-ALA-D activity in the livers and kidneys. SDH activity was diminished in the skeletal and cardiac muscles of this group.

These results indicated that exercise associated with dietary Se deficiency can inhibit the production of thiol-containing enzymes, delta-ALA-D and SDH, from different tissues; however, LDH activity was not changed. The decrease in enzyme activities can be tentatively attributed to oxidation of thiol groups by the reactive oxygen species produced by exercise.