Effects of thyroxine on the migration of hippocampal neurons in newborn rat exposed to HTO

Abstract

Objective To explore the effect of thyroxine (TH) on the migration of hippocampal neurons in newborn rat exposed to tritiated water (HTO).Methods The hippocampal neurons from neonatal rats were primarily cultured,7 days later,randomly divided into control group,HTO group,TH group and HTO + TH group(3.7 × 105 Bq/ml HTO and 0.3 μg/ml TH were simultaneously added).After 24 h,the distance of neuronal migration was measured with Leica AF 6000,the expressions of BDNF and Reelin mRNA in neurons were analyzed with reverse transcription polymerase chain reaction (RT-PCR),the expression of β-tubulin protein in neurons was assayed with Western blot and immunocytochemical staining.Results Compared with control group,the expression of Reelin mRNA,BDNF mRNA and β-tubulin in HTO group were significantly reduced(t =5.80,5.48,5.47,P ＜ 0.01),but those in HTO + TH group and TH group were obviously increased (t =7.75,12.06,13.65,P ＜ 0.01 ;t =4.34,5.47,5.65,P ＜0.01)and higher than that in HTO group (t =2.92,10.32,8.76,P ＜ 0.01 ;t =18.07,20.55,40.13,P ＜0.01).Accordingly,the neuronal migration distance in HTO group was much shorter than that in control (t =8.62,P ＜ 0.01),and in HTO + TH group and TH group was far longer than that in control(t =7.64,4.93,P＜0.01).Moreover,the neuronal migration distance in HTO + TH group was notably elongated in comparison with that in HTO group(t =11.32,12.31,P ＜ 0.01).Conclusions Thyroxine may promote the migration of hippocampal neurons in newborn rat exposed to HTO. Key words: Thyroxine; HTO irradiation; Neuron migration; β-tubulin; Brain derived neurotrophic factor