血管紧张素Ⅱ对胰岛细胞的作用

肾素-血管紧张素系统(RAS)包括循环RAS和局部RAS,其核心活性物质均为血管紧张素Ⅱ(AngⅡ).已证实胰岛局部存在RAS,并可不依赖于循环RAS独立合成AngⅡ.现在认为,胰岛局部RAS对胰岛细胞的内分泌功能调节起重要作用.AngⅡ和相应胞膜、胞浆内的不同AngⅡ受体结合后,通过改变血管收缩性而改变胰岛供血和局部氧张力,通过蛋白激酶通路等机制,影响胰岛素和生长抑素的分泌.但局部RAS的过度激活会使胰腺局部的活性氧簇牛成增多,导致胰岛细胞功能异常.促进胰岛细胞凋亡进程,参与胰岛局部炎性反应过程和胰腺的纤维化,同时在外周组织中介导胰岛素抵抗的产生,从而间接影响胰岛细胞功能.

Effects of angiotensin Ⅱ on islet cells

The systemic renin-angiotensin system (RAS) includes circulation RAS and local RAS.Of particularly important in local RAS is angiotensin Ⅱ as well as in circulation RAS.Existence of a local RAS is now proved in islet, which contains the biosynthesis of angiotensin Ⅱ imtependent of the circulation RAS.This islet RAS has been proposed to have important regulative effect on the endocrine activities of islet cells.When angiotensin Ⅱ binds to its different kinds of unique receptors on the cell membrane and in the cell cytoplasm, the local RAS will be actived.It may change the vascular contractility, affect islet blood flow as well as oxygen tension, by the protein kinase pathway and so on.As a result, the insulin biosynthesis and somatostatin secretion is changed.But the overactivation of islet RAS may drive the synthesis of reactive oxygen species, which will cause islet cells dysfunction and apoptosis, and hence be involved in the processes of pancrease inflammation and islet fibrosis.At the same time, it contributes to insulin resistance in the peripheral tissues, which takes effect on the islet cell functions mediately.