Interactions of nutrients, insulin-like growth factors (IGFs) and IGF-binding proteins in the regulation of DNA synthesis by isolated fetal rat islets of Langerhans.
Interactions of nutrients, insulin-like growth factors (IGFs) and IGF-binding proteins in the regulation of DNA synthesis by isolated fetal rat islets of Langerhans.
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营养物质、胰岛素样生长因子 (IGF) 和 IGF 结合蛋白在离体胎鼠朗格汉斯胰岛 DNA 合成调节中的相互作用。
DOI：
10.1677/joe.0.1380401
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发表时间：
1993
影响因子：
4
通讯作者：
D. Hill
中科院分区：
文献类型：
--
作者：
J. Hogg;V. Han;D. Clemmons;D. Hill
胰岛素是子宫内最佳组织生长和功能的主要调节激素。它对生长中的胎儿的持续可用性取决于胰岛细胞质量的增加。本研究的目的是研究营养物质的可利用性和胰岛素样生长因子（IGF）的释放和行动之间的相互作用，在DNA合成过程中分离的胎鼠胰岛。具体而言，我们希望确定（a）葡萄糖或总氨基酸的可用性是否改变内源性IGF-I或IGF-II的释放，（B）IGF-I和IGF-II是否都是胰腺β细胞的有效有丝分裂原，（c）胰岛是否释放IGF结合蛋白（IGFBPs）及其可能受营养素可用性的调节，以及（d）IGFBPs如何调节IGF改变胰岛DNA合成的能力。通过胶原酶消化从妊娠第22天的胎鼠胰腺分离胰岛。将经过5天预孵育方案后富含β细胞的胰岛维持在不同浓度的葡萄糖（1.4-16.7 mmol/l）或氨基酸（x1- x3总浓度）中，含或不含外源性IGF-I、-II、IGFBP-1或IGFBP-2。胰岛素和内源性IGF-I和-II的释放分别通过放射免疫测定法测定，IGFBP释放通过Western配体印迹分析表征。通过掺入[3 H]胸苷来测量DNA合成。分离的胰岛表现出响应于增加量的葡萄糖和氨基酸的胰岛素释放增加，证明了功能活力。这两类营养素也增加了胰岛的DNA合成率。胰岛释放的IGF-II几乎是其两倍（0.22 +/- 0.08 nmol/l，平均值+/- S.E.M.，n = 4）作为IGF-I（0.14 +/- 0.03 nmol/l）在含有8.7 mmol葡萄糖/l和x1氨基酸的培养物中。更低或更高浓度的葡萄糖不会改变IGF的释放，但在x2氨基酸存在下，IGF-II的释放显著增加（0.53 +/- 0.08 nmol/l，P < 0.01）。无论葡萄糖浓度如何，外源性IGF-I刺激胰岛DNA合成的活性（半数最大浓度（ED 50）1.6 +/- 0.4 nmol/l，n = 3）是IGF-II（ED 50 8.1 +/- 0.6 nmol/l）的5倍。分离的胰岛释放四种IGFBP，分子大小分别约为19，25，35和46 kDa。通过蛋白质免疫印迹将35 kDa形式鉴定为IGFBP-2。将葡萄糖浓度增加至1.4 mmol/l和16.7 mmol/l之间，导致19、25和35 kDa IGFBP物质的释放呈剂量相关性增加。（400字处截断摘要）
Insulin is a major regulatory hormone for optimal tissue growth and function in utero. Its continued availability to the growing fetus depends on increasing islet cell mass. The purpose of the study was to examine the interactions between nutrient availability and insulin-like growth factor (IGF) release and action during DNA synthesis by isolated fetal rat islets of Langerhans. Specifically, we wished to determine (a) whether the availability of glucose or total amino acids altered the release of endogenous IGF-I or -II, (b) if both IGF-I and -II were effective mitogens for pancreatic beta-cells, (c) whether islets released IGF-binding proteins (IGFBPs) and their possible regulation by nutrient availability and (d) how IGFBPs might regulate the ability of IGFs to alter islet DNA synthesis. Islets of Langerhans were isolated from fetal rat pancreata on day 22 of gestation by collagenase digestion. Islets enriched in beta-cells following a 5-day preincubation regime were maintained in various concentrations of glucose (1.4-16.7 mmol/l) or amino acids (x1- x3 total concentrations), with or without exogenous IGF-I, -II, IGFBP-1 or IGFBP-2. The release of insulin and endogenous IGF-I and -II were each determined by radioimmunoassay, and IGFBP release characterized by Western ligand blot analysis. DNA synthesis was measured by the incorporation of [3H]thymidine. Isolated islets demonstrated an increased release of insulin in response to increasing amounts of both glucose and amino acids, demonstrating functional viability. Both classes of nutrients also increased the DNA synthetic rate of islets. Islets released almost twice as much IGF-II (0.22 +/- 0.08 nmol/l, mean +/- S.E.M., n = 4) as IGF-I (0.14 +/- 0.03 nmol/l) in cultures containing 8.7 mmol glucose/l and x1 amino acids. Lesser or greater concentrations of glucose did not alter the release of either IGF, but the release of IGF-II was significantly increased (0.53 +/- 0.08 nmol/l, P < 0.01) in the presence of x2 amino acids. Exogenous IGF-I was fivefold more active in stimulating DNA synthesis by islets (half maximal concentration (ED50) 1.6 +/- 0.4 nmol/l, n = 3) than was IGF-II (ED50 8.1 +/- 0.6 nmol/l), regardless of glucose concentration. Isolated islets released four species of IGFBP with molecular sizes of approximately 19, 25, 35 and 46 kDa respectively. The 35 kDa form was identified by Western immunoblot as IGFBP-2. Increasing the glucose concentration between 1.4 mmol/l and 16.7 mmol/l caused a dose-related increase in the release of the 19, 25 and 35 kDa IGFBP species.(ABSTRACT TRUNCATED AT 400 WORDS)