Insulin secretion by rat lachrymal glands: effects of systemic and local variables
Insulin secretion by rat lachrymal glands: effects of systemic and local variables
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DOI：
10.1152/ajpendo.00469.2004
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发表时间：
2005-11-01
影响因子：
5.1
通讯作者：
Rocha, EM
中科院分区：
文献类型：
--
作者：
Cunha, DA;Carneiro, EM;Rocha, EM
为了了解胰岛素在泪膜中的分泌机制和生理作用，本研究检查了1）葡萄糖静脉刺激下泪膜中胰岛素分泌的时间过程，2）葡萄糖和卡巴胆碱诱导的离体泪腺（LG）的胰岛素分泌，3）胰岛素对角膜消耗葡萄糖的影响，以及4）胰岛素的表达，胰十二指肠同源框-1（PDX-1）和LG组织中的葡萄糖转运蛋白（GLUT）。在葡萄糖刺激后的最初几分钟内，8周龄雄性Wistar大鼠泪膜中的胰岛素水平从0.6 +/- 0.45增加到3.7 +/- 1.3 ng/ml。体外试验表明，较高的葡萄糖浓度从2.8至16.7 mM，200 μ M卡巴胆碱，或40 mM氯化钾显着增加胰岛素分泌的泪腺相比，控制，但没有检测到C-肽测定RIA。角膜组织的葡萄糖消耗，通过放射性标记D-[U-C-14]葡萄糖摄取评价，24.07 +/- 0.61，在6 nM胰岛素存在下，增加至31.63 +/- 3.15 nmol中心点角膜（-1）中心点2 h（-1）（P = 0.033）和37.5 +/- 3.7 nmol中心点角膜（-1）中心点2 h（-1）在11.2 mM葡萄糖的存在下（P = 0.015）。免疫组化结果显示，胰岛素和PDX-1 mRNA在LG细胞中均有表达，胰岛素定位于腺泡细胞的顶端区域，Western blot结果显示GLUT-1表达，而PDX-1无表达。这些发现表明，泪膜中的胰岛素分泌受局部刺激如营养和神经输入的影响，并且这种激素在眼表组织中起代谢作用。这些数据还表明，在正常条件下，LG分泌的胰岛素是储存的，但尚不清楚LG是否在本地产生。
To understand the secretory mechanisms and physiological role of insulin in the tear film, the present study examined 1) the time course of insulin secretion in the tear film under glucose intravenous stimulation, 2) the glucose- and carbachol-induced insulin secretion from isolated lachrymal gland (LG), 3) the effect of insulin on glucose consumption by the cornea, and 4) the expression of insulin, pancreatic duodenal homeobox-1 (PDX-1), and glucose transport proteins (GLUTs) in LG tissue. The insulin level in the tear film of 8-wk-old male Wistar rats increased from 0.6 +/- 0.45 to 3.7 +/- 1.3 ng/ml in the initial minutes after glucose stimulation. In vitro assays demonstrated that higher glucose concentrations from 2.8 to 16.7 mM, 200 mu M carbachol, or 40 mM KCl significantly increased insulin secretion from lacrimal glands compared with controls, but did not detect C-peptide as measured by RIA. Glucose consumption by corneal tissue, evaluated by radiolabeled D-[U-C-14] glucose uptake, was 24.07 +/- 0.61 and was enhanced to 31.63 +/- 3.15 nmol center dot cornea(-1) center dot 2 h(-1) in the presence of 6 nM insulin ( P = 0.033) and to 37.5 +/- 3.7 nmol center dot cornea(-1) center dot 2 h(-1) in the presence of 11.2 mM glucose ( P = 0.015). Insulin and PDX-1 mRNA was detected in LG. Insulin was located in the apical areas of acinar cells by immunoperoxidase and the expression of GLUT-1, but not PDX-1, was confirmed by Western blot. These findings suggest that insulin secretion in the tear film is influenced by local stimuli such as nutrient and neural inputs and that this hormone plays a metabolic role in ocular surface tissues. These data also indicate that under normal conditions the insulin secreted by LG is stored, but it is not clear that is locally produced in the LG.