Effects of voluntary resistance exercise on heme biosynthesis in rats given glucocorticoid-injections.

To identify the effects of a tower-climbing exercise on bone marrow heme biosynthesis and hematological status in rats given glucocorticoid-injections as a model of aging, 29 male Sprague-Dawley rats, 10 weeks of age, were assigned to three groups: a saline control (C, n = 9), a glucocorticoid-sedentary (GS, n = 10) group, and a glucocorticoid-exercise (GE, n = 10) group. The GS and GE groups were given 2 mg/kg prednisolone daily, and the C group was given 2 ml of saline daily, subcutaneously. Each group was meal-fed commercial rat chow isoenergetically and given free access to water for 8 weeks. The GE group were allowed to climb a 200-cm tower to drink water from a bottle set at the top of it. Weight gain during the 8-week experimental period was greater in the C group than in the GS and GE groups. The gastrocnemius and tibialis anterior muscles were heavier in the C group than in other groups. The hematological parameters were not influenced by glucocorticoid administration with or without climbing exercise. Bone marrow delta-aminolevulinic acid dehydratase activity was significantly higher in the GE group than in the C group. These results suggest that 8 weeks of climbing exercise increases heme biosynthesis without alteration of hematological status in rats given glucocorticoid-injections. Resistance exercise may be a preventive therapy for iron-deficiency anemia associated with aging.