The Eff ect of resistance training and growth hormone injection on circulating IGF1 and IGFBP3 levels in a rat model

Growth hormone has mitotic and antiapoptotic effects which may increase proliferationand transformation of cells when it is expressed aberrantly. This study investigated the effectsof resistance training and growth hormone injection on circulating IGF1, IGFBP3 levels andIGF1/IGFBP3 ratio in male Wistar rats. Thirtytwo male Wistar rats were randomly assignedto a control group (C, n = 8), a resistance training group (RT, n = 8), a growth hormone injectiongroup (GI, n = 8) and a resistance training + growth hormone injection group (RG, n = 8). The resistance training protocol comprised of climbing a ladder (5 days/week, 3 sets/5 reps)while carrying a weight suspended from the tail. The growth hormone (2 mg/kg/day, 5 days/week) was injected before an exercise session. Serum IGF1, IGFBP3 levels, and IGF1/IGFBP3 ratio were measured after 8 weeks. Oneway ANOVA analysis was used for comparisonof serum IGF1 and IGFBP3 levels between groups. Serum IGF1 levels and IGF1/IGFBP3ratio signifi cantly decreased, but serum IGFBP3 levels showed no significant change in theRT group compared to the C group. Also, both serum IGF1 and IGFBP3 levels and IGF1/IGFBP3 ratio in GI and RG groups significantly increased compared to the other groups. Inconclusion, resistance training decreases serum IGF1 levels and/or IGF1/IGFBP3 ratio innormal condition. On the other hand, the growth hormone injection with and without the resistancetraining increases serum IGF1 levels and IGF1/IGFBP3 ratio which could be notedas a condition with a higher risk of neoplasm.