OBJECTIVETo explore the protective effects of insulin-like growth factor-1(IGF-1) on the survival and apoptosis of cortical neurons of neonatal rat under oxidative stress and its significance.

METHODPrimary cortical neurons from newborn rat were cultured and the oxidative stress model was established. Then cells were randomly divided into IGF-1 group and control group. The concentration of LDH in supernatant was detected. Cell survival was determined with MTT assay and the expression of active Caspase-3 was measured using Western Blotting.

RESULT(1) The values of LDH gradually decreased with the increasing IGF-1 added to the cells [(0.5065 ± 0.0064) to (0.435 ± 0.0065), (P < 0.01)], but when the concentration of IGF-1 reached a certain level (> 25 ng/ml), there were no longer obvious effects on the level of LDH [(0.42 ± 0.012) to (0.418 ± 0.0098), (P > 0.05)]; Western blot showed that the level of active Caspase-3 was significantly decreased after treatment with IGF-1 [(0.662 ± 0.033) to (0.199 ± 0.01), (P < 0.01)]. (2) Compared with control group, without or with low concentration of H2O2 (0 - 40 µM), the values of LDH and the expression of active Caspase-3 in IGF-1 group were significantly decreased[(1.518 ± 0.137) to (1.068 ± 0.067), (P < 0.05) and 0.850 ± 0.042 to 0.597 ± 0.03, P < 0.01, respectively] while the values of MTT obviously elevated [(0.773 ± 0.062) to (1.196 ± 0.057), (P < 0.05)]; but with higher concentration (≥ 60 µM) of H2O2, the values of LDH and MTT and the expression of active Caspase-3 in IGF-1 group all had no significant difference (P > 0.05). (3) When the concentration of H2O2 reached 60 µM and higher, whatever concentration of IGF-1 could not lower the level of LDH compared with control group [(2.376 ± 0.04) to (2.442 ± 0.046), (P > 0.05)].

CONCLUSIONSOxidative stress can induce IGF-1 resistance of cortical neurons in neonatal rat, and even increasing the concentration of IGF-1 can not restore their sensitivity to IGF-1.