Carlsson P O, Berne C, Jansson L
Department of Medical Cell Biology, Uppsala University, Sweden.
Diabetologia. 1998 Feb;41(2):127-33. doi: 10.1007/s001250050880.
An intrinsic angiotensin system has been described in the pancreas, with angiotensin II specific receptors being present on both exocrine, endocrine and vascular cells. The aim of the present study was to evaluate the effects of angiotensin II on insulin secretion and blood flow regulation in the pancreas. Blood flows were determined with a microsphere technique. Infusion of angiotensin II induced a dose-dependent reduction in both whole pancreatic and islet blood flow, which was most pronounced in the former. Administration of enalaprilate, an inhibitor of angiotensin-converting enzyme, and saralasin, a nonselective angiotensin II receptor antagonist, preferentially increased islet blood flow. The effects of angiotensin II on insulin release were examined by measuring insulin concentrations in the effluents from isolated perfused pancreata. In these preparations, enalaprilate affected neither basal nor glucose-stimulated insulin release, whereas angiotensin II delayed the first phase of insulin release in response to glucose. The effect of angiotensin II was probably due to initial marked vasoconstriction. The retardation of insulin release could be avoided by adding angiotensin II to the perfusion medium 20 min before glucose administration, i. e. so that the vasoconstriction had disappeared when glucose-stimulation began. The present study suggests that the angiotensin-system is important in regulation of islet blood flow and points to a pivotal role of islet blood perfusion for an adequate insulin release.
胰腺中已发现存在一种内在的血管紧张素系统，外分泌细胞、内分泌细胞和血管细胞上均有血管紧张素 II 特异性受体。本研究旨在评估血管紧张素 II 对胰腺胰岛素分泌和血流调节的影响。采用微球技术测定血流量。输注血管紧张素 II 可导致全胰腺和胰岛血流量呈剂量依赖性减少，其中全胰腺血流量减少最为明显。给予血管紧张素转换酶抑制剂依那普利拉和非选择性血管紧张素 II 受体拮抗剂沙拉新后，胰岛血流量优先增加。通过测量离体灌注胰腺流出液中的胰岛素浓度，研究血管紧张素 II 对胰岛素释放的影响。在这些实验制剂中，依那普利拉对基础胰岛素释放和葡萄糖刺激的胰岛素释放均无影响，而血管紧张素 II 则延迟了对葡萄糖刺激的胰岛素释放的第一阶段。血管紧张素 II 的作用可能是由于最初明显的血管收缩。在葡萄糖给药前 20 分钟将血管紧张素 II 添加到灌注培养基中，即当葡萄糖刺激开始时血管收缩已经消失，这样就可以避免胰岛素释放的延迟。本研究表明，血管紧张素系统在胰岛血流调节中起重要作用，并指出胰岛血流灌注对充分的胰岛素释放起关键作用。
