The Effect of rhGH and IGF-1 on Mitochondrial Superoxide Generation in Human Lymphocytes in Vitro

Growth Hormone (GH) and its mediator Insulin-like Growth Factor-1 (IGF-1) induce specific anabolic and broader metabolic effects, which are regarded as beneficial when they are present at physiological concentrations. However, for athletes looking to obtain a performance enhancing effect, the administration of high doses of these hormones could have negative health implications.
PURPOSE: To determine whether GH and IGF-1 exert a direct effect on the production of free radicals in mitochondria over a range of physiological and supraphysiological concentrations in the lymphocytes of healthy human subjects.
METHODS: Blood was collected from the antecubital vein of ten healthy male subjects (mean ± SD: age = 23 ± 4 yr, height = 1.78 ± 0.06 m, body mass = 77.1 ± 6.17 kg). Peripheral Blood Mononuclear Cells (PBMCs) were isolated from whole blood by density gradient centrifugation and resuspended in RPMI 1640 culture medium at a concentration of 1*106 cells/mL. Isolated cells were subsequently incubated for four hours in the presence of recombinant human growth hormone (rhGH) (Range = 0.5 - 100ng/mL) and IGF-1 (Range = 100 - 600ng/mL). Following treatment cells were analysed for the presence of superoxide by flow cytometry using the mitochondria targeted derivative of the fluorogenic probe hydroethidine (Mito-HE). All data is presented as mean ± SEM.
RESULTS: Mean fluorescence intensity was significantly reduced compared to control samples (20.75 ± 0.72 AU) at GH concentrations of 5ng/mL (13.57 ± 1.34 AU, p=0.03) and 10ng/mL (12.34 ± 1.54 AU, p=0.024), but not at supraphysiological concentrations of 50ng/mL and 100ng/mL (13.63 ± 1.7 AU, p=0.139 and 14.37 ± 2.19 AU, p=0.583 respectively). IGF-1 did not exert any significant effect on mitochondrial superoxide generation.
CONCLUSION: At physiological concentrations growth hormone elicits a protective effect against mitochondrial derived oxidative stress in vitro.