GLUCOSE TRANSPORTER GENE EXPRESSION IN RAT EMBRYO AND ITS REGULATION IN THE DIABETIC STATE

我们已经证明，高血糖诱导的胚胎病可能是由葡萄糖积累增加导致胚胎肌醇消耗介导的（Diabetologia 33: 597, 1990）。本研究旨在探讨葡萄糖转运蛋白（GLUT）在糖尿病早期器官发生过程中的表达及其调控。通过Northern和Western blot分析，GLUT-1 mRNA和蛋白在胚胎器官发生早期均有高表达，在妊娠第10天（神经管形成的主要时期）达到峰值。免疫组化染色显示GLUT-1蛋白主要分布于神经管组织，并定位于神经上皮细胞的质膜。在链脲佐菌素诱导的糖尿病大鼠胚胎中，即使在糖尿病条件下，谷氨酸-1 mRNA和蛋白的高表达水平在第10天仍持续存在。为了检测葡萄糖转运体基因和蛋白的表达是否在极端高血糖时受到抑制，将胚胎在高糖培养基（720和1320 mg/dl）中培养24 h（第9-10天）。在高血糖（39.9mM和73.3mM）培养24 h（第9-10天）时，GLUT-1 mRNA和蛋白的表达均未下调。此外，糖尿病状态也未改变神经管中GLUT-1的染色强度和细胞分布。尽管在糖尿病环境下，葡萄糖转运蛋白的高表达可能在高血糖诱导的神经管缺陷中发挥作用，通过允许葡萄糖增加进入神经上皮细胞，导致胚胎肌醇消耗。

We have shown that hyperglycemia-induced embryopathy could be mediated by myo-inositol depletion of embryo as a result of increased accumulation of glucose (Diabetologia 33 : 597, 1990). The present study was performed to investigate glucose transporter (GLUT) expression during early organogenesis and its regulation in the diabetic conditions. Both GLUT-1 mRNA and protein, by Northern and Western blot analysis, were highly expressed in embryo during early organogenesis, reaching peak levels on day 10 of gestation (the main period of neural tube formation). Immunohistochemical staining showed that GLUT-1 protein was predominantly distributed in the tissue of neural tube and noted to be localized at the plasma membrane of the neuroepithelial cell. High expression of GLUT-1 mRNA and protein levels persisted in the embryo on day 10 even in the diabetic conditions in streptozotocin-induced diabetic rats. To test whether the expression of glucose transporter gene and protein was suppressed during extreme hyperglycemia, embryos were cultured in high glucose medium (720 and 1320 mg/dl) for 24 h (Day 9-10). The expression of GLUT-1 mRNA and protein were not down-regulated in culture of hyperglycemia (39.9mM or 73.3mM) for 24 h (Day 9-10). Furthermore, the diabetic states did not change also the staining intensity and cellular distribution of the GLUT-1 in the neural tube during the period of neurulation. High expression of the glucose transporter despite the diabetic environment may play a role in hyperglycemia-induced neural tube defects, by permitting increased entry of glucose into neuroepithelial cells, leading to myo-inositol depletion of embryo.