ACTA ENDOCRINOLOGICA (BUC)

Context and objective. In this study, we aimed to investigate how moderate physical activity improves the bone ultrastructural parameters in rats with glucocorticoidinduced secondary osteoporosis. Animals and Methods. Research has been carried out on Wistar female rats. Secondary osteoporosis was induced through daily i.m.1.5 mg/kgbw methylprednisolone, over a period of 30 days. A group of rats with induced secondary osteoporosis were subjected to physical activity (swimming) for one hour/day for 30 days. Rats were sacrificed 24 hours after the last administration and femoral bones were used for electron microscopy analysis. Results. The ultrastructural findings obtained from the rats with osteoporosis showed varying degrees of alteration in all cellular components. A moderate physical effort led to the overall maintenance of the normal ultrastructure of the cells and connective components, protecting the lamellar structure of the compact bone from the deleterious effects of glucocorticoid. The shape and components of osteocytes were also preserved and the accumulation of lipids in the bone marrow diminished. Conclusions. Physical exercise has been shown to have a protective role by lowering the development of structural alterations specific to osteoporosis. Therefore, moderate physical exercises are recommended for improving the structure of the bone mass affected by glucocorticoid treatment.