Ontogenesis of insulin processing in fetal rat hepatocytes.
Ontogenesis of insulin processing in fetal rat hepatocytes.
复制标题
胎鼠肝细胞中胰岛素加工的本体发生。
DOI：
10.1007/bf00400194
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发表时间：
1991
期刊：
影响因子：
8.2
通讯作者：
Richman,RA
中科院分区：
文献类型：
--
作者：
Benedict,MR;Richman,RA
我们研究了从妊娠17、19和21天的大鼠胎儿中分离的培养肝细胞中的胰岛素加工和肝糖生成。稳态胰岛素结合率在妊娠第17 - 19天增加了250%，从145±8增加到361±52 fmol/mg蛋白，到妊娠第21天增加了40%（405±69 fmol/mg蛋白）。在37°C下，125 I-胰岛素被所有三个年龄段的肝细胞迅速内化（t1/2<5 min），15 min时达到最大水平（总细胞相关放射性的63-76%）。125 I-标记的降解产物在细胞内迅速出现（t1/2<15 min）。然而，即使在37°C下4小时后，大部分（68-77%）细胞内放射性仍由完整的125 I-胰岛素组成。肝细胞预先加载125 I-胰岛素，然后酸剥离表面结合的放射性，迅速释放完整的125 I-胰岛素（逆向内吞作用）及其放射性标记的降解产物。虽然完整胰岛素最初释放更快（t1/2<6 min），并在15-30 min后达到平台期，但降解产物在培养基中继续积累至少4 h。甲胺抑制细胞内125 I-胰岛素降解在所有三个胎龄，也阻断胰岛素刺激的糖原在19和21天的肝细胞，而不改变基础糖原合成。在对照或甲胺处理的培养物中，17天胎鼠肝细胞中未诱导胰岛素刺激的糖原生成。我们的结论是，降解和retroendocytotic途径处理胰岛素存在于胎鼠肝细胞妊娠17天。此外，在19天和21天的胎鼠肝细胞中，胰岛素受体加工功能与胰岛素的糖原生成作用相关
We studied insulin processing and hepatic glycogenesis in cultured hepatocytes isolated from rat fetuses of 17, 19, and 21 days of gestation. Steady-state insulin binding increased by 250% between days 17 and 19, from 145±8 to 361±52 fmol/mg protein, and by an additional 40% (405±69 fmol/mg protein) by 21 days of gestation. At 37°C,125I-insulin was rapidly (t1/2<5 min) internalized by hepatocytes at all three ages, reaching maximal levels (63–76% of the total cell-associated radioactivity) by 15 min.125I-labelled degradation products appeared rapidly (t1/2<15 min) within the cells. Yet, the majority (68–77%) of the intracellular radioactivity consisted of intact125I-insulin, even after 4 h at 37°C. Hepatocytes pre-loaded with125I-insulin and then acid-stripped of surface-bound radioactivity, rapidly released both intact125I-insulin (retroendocytosis) and its radiolabelled degradation products. While intact insulin was initially released more rapidly (t1/2<6 min), and reached a plateau after 15–30 min, the degradation products continued to accumulate in the medium for at least 4 h. Methylamine inhibited intracellular125I-insulin degradation at all three gestational ages and also blocked insulin-stimulated glycogenesis in 19- and 21-day hepatocytes, without altering basal glycogen synthesis. Insulin-stimulated glycogenesis was not induced in 17-day fetal rat hepatocytes in control or methylamine-treated cultures. We conclude that both degradative and retroendocytotic pathways for processing insulin are present in fetal rat hepatocytes by 17 days of gestation. Further, insulin-receptor processing was functionally related to the glycogenic action of insulin in responsive 19- and 21-day fetal rat hepatocytes