Uptake of IGF-I is not mediated by IGF-IR. Pre-incubation with a molar excess of Des(1–3)IGF-I (100 ng/ml), which does not bind to IGFBPs, does not block the uptake of 125I-IGF-I (20 ng/ml) into the brain. Pre-incubation with unlabeled IGF-I (20 ng/ml), which binds both to IGF-IR and IGFBPs, blocks 125I-IGF-I (20 ng/ml) uptake into the brain (*). Results are mean ± S.D. n = 6; *p < 0.05 by ANOVA 125I-IGF-I versus IGF-I + 125I-IGF-I and IGF-I + Des(1–3)IGF-I + 125I-IGF-I.
Fletcher et al. BMC Neuroscience 2013 14:158 doi:10.1186/1471-2202-14-158