Effects of whole-body irradiation on contractile proteins of skeletal muscle in rats submitted to early malnutrition

Using an animal model, this study was designed to evaluate long-term effects of ionizing radiation to the contractile proteins (actin and myosin) of two different skeletal muscles, Soleus and Extensor Digitorum Longus (EDL) in rats with early malnutrition. For this, Wistar rats were divided into four groups: Normal nourished; Malnourished; Irradiated-Normal nourished and Irradiated-Malnourished, composed of nine animals each group. According to the group to which they belonged, for the simulation of perinatal malnutrition was employed diet to 8% casein, while in relation to the groups of animals that were submitted to TBI (Total Body Irradiation) the protocol used was the exposure, after 28 days, with a single dose of 2.5 Gy, from a cobalt-60 source (dose rate: 75 cGy / min). At 90 days of age, all animals were sacrificed by decapitation, followed by blood collection and removal of the muscles. Serum proteins were quantified by Biuret method and Bromocrezol Green, while expression of muscle contractile proteins were measured by the technique of Western blotting. The data were subjected to homogeneity and normality tests, Student's t-test and analysis of two-dimensional variance (ANOVA two-ways) followed by Tukey's multiple comparison test. The results showed that: both TBI and malnutrition caused loss of body weight; isolatedly, TBI led to a reduction in the concentration of serum proteins; malnutrition caused an increase in myosin-I expression in Soleus and EDL muscles; TBI caused an increase in myosin-IIB expression in Soleus and EDL muscles; malnutrition and TBI acting together provoked an increase in myosin-IIB expression in EDL muscle. This research points to the need for more detailed studies with different doses at different ages, in order thus, extrapolate for children and young people who are submitted to treatment involving TBI, in the sense to prevent pathological conditions in adulthood and minimize the deleterious effects of ionizing radiation on muscle function. (author)