Different effect of the nitric oxide synthase inhibition between the cortical and trabecular bone of osteoporotic female rats submitted or no the physical activity

Introduction. - The objective of this study was to verify the participation of the nitric oxide as mediator of the effects of the physical activity on the cortical and trabecular bone in the osteoporotic rats with the nitric oxide synthase inhibition. Syntesis. - Thirty Wistar female rats divided into six groups were used: (1) sham-operated; (2) sedentary osteoporotic; (3) active osteoporotic; (4) sham-operated with L-NAME; (5) sedentary osteoporotic with L-NAME; and (6) active osteoporotic with L-NAME. The trabecular bone percentage in all of the bones and the cortical thickness of the vertebral segments were measured. The means were compared by SNK test. Results. - The nitric oxide synthase inhibition reduced of the cortical thickness in cervical and thoracic vertebrae of the sham-operated rats (normal). The sedentary osteoporotic group presented decrease of the trabecular bone percentage in the whole skeleton. The administration of L-NAME in the sedentary osteoporotic group caused different effect: increased the trabecular bone percentage in the long bones, and in the thoracic and lumbar vertebrae, and reduced the cortical thickness of the vertebrae. The physical exercise increased the bone mass of the cortical and trabecular bone in osteoporotic rats. But L-NAME impeded the increase of trabecular and cortical bone promoted by the physical activity in the tibia and in the first thoracic vertebrae of the osteoporotic rats. Conclusion. - The nitric oxide is a mediator of the beneficial effects of physical activity upon bone mass in rats with osteoporosis and the nitric oxide synthase inhibition promoted different effect between the cortical and trabecular bone. (C) 2010 Elsevier Masson SAS. All rights reserved.