The Eff ect of resistance training and growth hormone injection on circulating IGF-1 and IGFBP-3 levels in a rat model

Growth hormone has mitotic and anti-apoptotic eff ects which may increase proliferation and transformation of cells when it is expressed aberrantly. Th is study investigated the eff ects of resistance training and growth hormone injection on circulating IGF-1, IGFBP-3 levels and IGF-1/IGFBP-3 ratio in male Wistar rats. Th irty-two male Wistar rats were randomly assigned to a control group (C, n = 8), a resistance training group (RT, n = 8), a growth hormone injection group (GI, n = 8) and a resistance training + growth hormone injection group (RG, n = 8). Th e resistance training protocol comprised of climbing a ladder (5 days/week, 3 sets/5 reps) while carrying a weight suspended from the tail. Th e growth hormone (2 mg/kg/day, 5 days/ week) was injected before an exercise session. Serum IGF-1, IGFBP-3 levels, and IGF-1/IGFBP- 3 ratio were measured aft er 8 weeks. One-way ANOVA analysis was used for comparison of serum IGF-1 and IGFBP-3 levels between groups. Serum IGF-1 levels and IGF-1/IGFBP-3 ratio signifi cantly decreased, but serum IGFBP-3 levels showed no signifi cant change in the RT group compared to the C group. Also, both serum IGF-1 and IGFBP-3 levels and IGF-1/ IGFBP-3 ratio in GI and RG groups signifi cantly increased compared to the other groups. In conclusion, resistance training decreases serum IGF-1 levels and/or IGF-1/IGFBP-3 ratio in normal condition. On the other hand, the growth hormone injection with and without the resistance training increases serum IGF-1 levels and IGF-1/IGFBP-3 ratio which could be noted as a condition with a higher risk of neoplasm.