Efeito da associação de Ginkgo biloba e exercício físico no tratamento da osteoporose induzida por glicocorticoides em ratas

Abstract

Osteoporosis is a systemic disorder characterized by decreased bone mineral density (BMD), with deterioration of bone microarchitecture, leading to increased skeletal fragility and fracture risk. Treatment of osteoporosis involves the use of bisphosphonates, calcitonin, PTH replacement, therapy and exercise. However, several in vitro studies have shown that Ginkgo biloba extract (EGb 761) and its components showed estrogenic agonist action, and contributes to cellular defense mechanism against cellular proliferation, initiation and progression of cancer. Thus, the present study evaluated the effect of the extract of G. biloba in dosages of 14, 28 and 56mg/Kg/day and its association with the protocol of swimming exercise on glucocorticoid-induced osteoporosis in adult rats by histopathology, immunohistochemistry (detection of calcium by the Von Kossa stain), biochemistry (serum calcium, alkaline phosphatase and molar concentration of hydroxyproline) and quantitative computed tomography. The induction of osteoporosis was effected by administration of dexamethasone at dose of 7mg/kg for 5 weeks. As a positive control we used the sodium alendronato at dose of 0.2 mg/kg/day. The evaluations were performed at 1 °, 25 ° and 50 ° days of treatment. The results showed that lower doses of the extract with or without a swimming protocol showed similar results to those observed in control animals and the ones treated with sodium aledronato, but the highest dosage of the extract without the associating of the swimming protocol caused hypercalcemia at 25th day, and on the 50th day when associated with swimming protocol. It is concluded that the extract of G. biloba isolated or associated with a swimming protocol at doses of 14 and 28mg/Kg reverts induced osteoporosis in rats. However, more studies are necessary in order to better comprehend the effect of dose/time of this extract with or without a physical activity in the pathology of osteoporosis and its possible consequences on the physiology of other systems.