Thong Farah S L, Lally Jamie S V, Dyck David J, Greer Felicia, Bonen Arend, Graham Terry E
Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada.
Appl Physiol Nutr Metab. 2007 Aug;32(4):701-10. doi: 10.1139/H07-039.
The A1 adenosine receptor (A1AR) has been suggested to participate in insulin- and contraction-stimulated glucose transport in skeletal muscle, but the qualitative and quantitative nature of the effect are controversial. We sought to determine if A1AR is expressed in rat soleus muscle and then characterize its role in glucose transport in this muscle. A1AR mRNA and protein expression were determined by RT-PCR and Western blotting, respectively. To examine the role of adenosine in 3-O-methylglucose transport, isolated muscles were exposed to adenosine deaminase and alpha,beta-methylene adenosine diphosphate to remove endogenous adenosine and were left unstimulated (basal) or stimulated with insulin. To assess the functional participation of A1AR in 3-O-methylglucose transport, muscles were incubated with A1-selective agonist and (or) antagonist in the absence of endogenous adenosine and with or without insulin. A1AR mRNA was expressed in soleus muscle and A1AR was present at the plasma membrane. Removal of endogenous adenosine reduced glucose transport in response to 100 microU/mL insulin (approximately 50%). The A1-selective agonist, N6-cyclopentyladenosine, increased submaximal (100 microU/mL) insulin-stimulated glucose transport in a dose-dependent manner (0.001-1.0 micromol/L). This stimulatory effect was inhibited by the A1-selective receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine in a concentration-dependent manner (0.001-1.0 micromol/L). However, neither activation nor inhibition of A1AR altered basal or maximal (10 mU/mL) insulin-stimulated glucose transport. Our results suggest that adenosine contributes approximately 50% to insulin-stimulated muscle glucose transport by activating the A1AR. This effect is limited to increasing insulin sensitivity, but not to either basal or maximal insulin-stimulated glucose uptake in rat soleus muscle.
A1腺苷受体（A1AR）被认为参与骨骼肌中胰岛素和收缩刺激的葡萄糖转运，但其作用的性质和程度存在争议。我们试图确定A1AR是否在大鼠比目鱼肌中表达，然后表征其在该肌肉葡萄糖转运中的作用。分别通过逆转录聚合酶链反应（RT-PCR）和蛋白质免疫印迹法测定A1AR信使核糖核酸（mRNA）和蛋白质表达。为了研究腺苷在3-O-甲基葡萄糖转运中的作用，将分离的肌肉暴露于腺苷脱氨酶和α,β-亚甲基腺苷二磷酸以去除内源性腺苷，使其处于未刺激（基础）状态或用胰岛素刺激。为了评估A1AR在3-O-甲基葡萄糖转运中的功能参与，在没有内源性腺苷的情况下，肌肉与A1选择性激动剂和（或）拮抗剂一起孵育，同时有或没有胰岛素。A1AR mRNA在比目鱼肌中表达，且A1AR存在于质膜上。去除内源性腺苷可降低对100微单位/毫升胰岛素的葡萄糖转运反应（约50%）。A1选择性激动剂N6-环戊基腺苷以剂量依赖性方式（0.001 - 1.0微摩尔/升）增加次最大（100微单位/毫升）胰岛素刺激的葡萄糖转运。这种刺激作用被A1选择性受体拮抗剂1,3-二丙基-8-环戊基黄嘌呤以浓度依赖性方式（0.001 - 1.0微摩尔/升）抑制。然而，A1AR的激活或抑制均未改变基础或最大（10毫单位/毫升）胰岛素刺激的葡萄糖转运。我们的结果表明，腺苷通过激活A1AR对胰岛素刺激的肌肉葡萄糖转运贡献约50%。这种作用仅限于增加胰岛素敏感性，而不影响大鼠比目鱼肌基础或最大胰岛素刺激的葡萄糖摄取。
