The radio-protective effects of melatonin on the radiation-damaged bones

In this study, the radio-protective effects of melatonin on the radiation-damaged bones were investigated comparatively with the amifostin. For this purpose some biomechanical parameters of bones such as the ultimate displacement, ultimate force, stiffness, energy absorption capacity, young modulus, toughness, ultimate stress, ultimate strain and some geometric parameters such as bone mineral density, bone mineral content and cortical area of bone were investigated.Fort this purpose, 40 female Sparague Dawley rats were used. Animals were divided into 5 groups. These are control group (C, n=8, saline, 1 ml i.p.), radiation (R, n=8, saline, 1 ml i.p.), radiation + melatonin 25 (R+M25, n=8, 25 mg/kg, i.p.), radiation + melatonin 50 (R+M50, n=8, 50 mg/kg i.p.) and radiation + amifostisin (R+WR, n=8, 200 mg/kg i.p.). A single dose of 50 Gy gamma radiation was exposed to the left legs of the rat groups of R, R+M25, R+M50 and R+WR.Looking at a weekly live weight of animals, a significant reduction was observed in body weight of radiation groups (R, R+M25, R+M50 and R+WR). During the experiment, no any changes in the femur area of control group but much hair loss and skin lesions have been seen in rats that radiation treated.At the end of a four-week of experiment, measurements were done on the left femur of each rat using biomechanical and densitometric methods. Bone mineral density was calculated by dual energy X-ray absorptiometry, while the cortical area of bone was measured by computed tomography.In the measurements, BMD value of group R showed a decrease according to K group, while BMD value of R+M25 showed an increase both according to R and K groups. No any differences obtained between R+M50 and R+WR groups with K groups. Although BMC value of R+M25 and R+M50 groups showed no significant differences between K and R groups, R+WR group showed significant differences according to R group.In the result of biomechanical analyzes, all parameters except for the young modulus of the R group, a decreasing were observed. R+M25 and R+M50 groups, the parameters such as ultimate displacement, ultimate force, stiffness, and ultimate stress, ultimate strain were decreased according to K group but the ultimate displacement, ultimate force, toughness and energy absorption capacity parameters for R+M25 according to R group were increased statistically. In the all the parameters, application of 50 mg/kg of melatonin showed less effects compared to those given for 25 mg/kg of melatonin were observed. In the R+WR group, the ultimate displacement, ultimate force and energy absorption capacity increased those compared to R group, while the young modulus and toughness increased, Ultimate force and stiffness showed decreasing according to K group.According to these results, radiation treated to the rats reduce the bone quality, however application of melatonin showed a protective effect on bone structure same as Amifostin application.