Insulin-stimulated alpha-(methyl)aminoisobutyric acid uptake in skeletal muscle. Evidence for a short-term activation of uptake independent of Na+ electrochemical gradient and protein synthesis.
Insulin-stimulated alpha-(methyl)aminoisobutyric acid uptake in skeletal muscle. Evidence for a short-term activation of uptake independent of Na+ electrochemical gradient and protein synthesis.
复制标题
胰岛素刺激骨骼肌中α-（甲基）氨基异丁酸的摄取。
作者：
A. Gumà;X. Testar;M. Palacín;A. Zorzano
1. 本研究旨在探讨胰岛素通过系统A类似物-（甲基）氨基异丁酸（MeAIB）刺激指长伸肌（EDL）氨基酸运输系统A的机制。2. 胰岛素刺激MeAIB摄取仅在孵育30分钟后就被注意到，并在60分钟时达到最大。胰岛素对MeAIB摄取的影响动力学表现为Vmax的增加。不修改MeAIB的Km。3. EDL肌肉用环己亚胺孵育90分钟，无论是否存在胰岛素，都不会改变MeAIB的摄取，这表明胰岛素的作用与蛋白质从头合成无关。用环己亚胺孵育180分钟导致MeAIB基础摄取减少；然而，胰岛素对氨基酸转运的刺激百分比没有改变。培养180分钟后，MeAIB的基础摄取增加，但在这些条件下，胰岛素的百分比效应没有变化。4. 瓦巴因、革兰霉素D或两者均可显著降低EDL肌对MeAIB的基础摄取，但胰岛素的百分比效应不变。5. 我们得出的结论是，胰岛素对氨基酸通过肌肉系统A转运的作用是迅速的，其特征是Vmax增加。，并且不依赖于蛋白质从头合成和Na+电化学梯度。我们的数据与胰岛素直接作用于系统A转运体是一致的。
1. The present study was designed to explore the mechanisms by which insulin stimulates system A of amino acid transport in extensor digitorum longus (EDL) muscles, by using a system A analogue, alpha-(methyl)aminoisobutyric acid (MeAIB). 2. Insulin stimulation of MeAIB uptake was noted after only 30 min of incubation and was maximal at 60 min. Kinetics of the insulin effect on MeAIB uptake were characterized by an increased Vmax. without modification of Km for MeAIB. 3. Incubation of EDL muscles with cycloheximide for 90 min did not modify MeAIB uptake in either the presence or the absence of insulin, indicating the independence of insulin action from protein synthesis de novo. Incubations for 180 min with cycloheximide caused a decrease in basal MeAIB uptake; however, the percentage stimulation of amino acid transport by insulin was unaltered. Basal MeAIB uptake was increased by incubation for 180 min, but under these conditions no change in the percentage effect of insulin was found. 4. Ouabain, gramicidin D, or both, markedly decreased basal MeAIB uptake by EDL muscle, but the percentage effect of insulin was unaltered. 5. We conclude that insulin action on amino acid transport through system A in muscle is rapid, is characterized by an increased Vmax., and is independent of protein synthesis de novo and the Na+ electrochemical gradient. Our data are compatible with insulin acting directly on the system A transporter.