大鼠胰腺发育过程中胰岛素释放功能完善的研究

The functional maturation of insulin secretion during pancreatic development in rat

目的:明确大鼠胰腺发育不同时期胰岛素合成及释放相关基因的表达差异,探讨胰岛素分泌功能完善的过程。方法:分离并提取SD大鼠胚胎发育12.5天(E12.5)、E15.5、E18.5、新生、出生后21天及成年大鼠胰腺组织,利用Affymetrix公司的高密度寡核苷酸芯片检测大鼠发育各阶段胰腺组织基因表达谱并分析胰岛素合成及释放相关基因的特异及差异表达情况。分别进行正常新生鼠、成年鼠血糖水平及正常新生第1、3、7、10、12天大鼠腹腔葡萄糖耐量试验(IPGTT)。采用ELISA法测定新生鼠和成年鼠血中胰岛素浓度。新生大鼠胰岛细胞原代培养观察新生鼠胰岛细胞的形态。结果:在胰岛素合成及释放相关基因中,胰岛素基因及其特异性转录因子如PDX-1在大鼠E12.5～E15.5时即开始有表达,以后胰岛素基因持续存在且表达增多;胰岛素胞吐过程中的关键基因Syntaxin-1a、Vamp-2、Rab-3a、Munc13-1等从E15.5开始出现,以后表达量亦增多;而葡萄糖刺激的胰岛素分泌(GSIS)相关基因中,葡萄糖转运体-2(Glut2)在胚胎早期开始表达,葡萄糖激酶(GCK)在胚胎中晚期才表达。自E18.5即检测到大鼠血中胰岛素的存在,随着胚胎的发育,血胰岛素浓度逐渐升高。新生大鼠对葡萄糖负荷不能耐受,出现IPGTT异常,出生1周以后IPGTT才逐渐趋于正常。新生鼠的胰岛形态与成年鼠相似,但体积相对较小,透亮度稍差。结论:大鼠胚胎胰腺发育早中期即已具备胰岛素合成及分泌的能力,但新生鼠刚出生时,其胰岛功能仍尚未完善,出生以后才逐渐对葡萄糖负荷有良好的反应性。

Objective：To define key genes relevant to insulin synthesis and exocytosis,and further to investigate the improved process of insulin secretion.Methods：Pancreata of SD rats at embryonic day 12.5（E12.5）,E15.5,E18.5 and newborn,21 days after birth,adult rats were dissected respectively.Genechips from Affymetrix company were applied to explore gene expression profiles.Some genes related to insulin synthesis and secretion were verified by real-time PCR.Intraperitoneal glucose tolerance tests （IPGTT） and ELISA were done to detect the function of pancreatic islet.Islet cells of newborn and adult rats were cultured to observe its shape.Results：Among genes related to insulin synthesis and release,insulin and relevant transcription factors such as PDX-1 began to express from E12.5;Munc13-1,Syntaxin-1a,Rab3a,Vamp-2,Glut-2 began to express from E15.5,while GCK expressed at late stage of embryonic day.Basic blood insulin level was detected at E18.5 and increased rapidly thereafter.However,in response to a glucose load,newborn rats were glucose intolerant,only rats older than a week began to show normal insulin secretory response gradually.The shape of islet cell in newborn rats was similar to adult one,but was much smaller and not so bright.Conclusion：Potential ability of insulin synthesis and release in rat occurs from early and middle stages of pancreatic development.But the normal insulin secretion response to glucose challenge starts later.