Ma X, Chapleau M W, Whiteis C A, Abboud F M, Bielefeldt K
Department of Internal Medicine, The Cardiovascular Center, University of Iowa College of Medicine, Iowa City, Iowa, USA.
Circ Res. 2001 Apr 27;88(8):787-93. doi: 10.1161/hh0801.089542.
Angiotensin II (Ang II) increases renal sympathetic nerve activity in anesthetized mice before and after ganglionic blockade, suggesting that Ang II may directly activate postganglionic sympathetic neurons. The present study directly tested this hypothesis in vitro. Neurons were dissociated from aortic-renal and celiac ganglia of C57BL/6J mice. Cytosolic Ca(2+) concentration (Ca(2+)) was measured with ratio imaging using fura 2. Ang II increased Ca(2+) in a subpopulation of sympathetic neurons. At a concentration of 200 nmol/L, 14 (67%) of 21 neurons responded with a rise in Ca(2+). The Ang II type 1 (AT(1)) receptor blocker (losartan, 2 micromol/L) but not the Ang II type 2 (AT(2)) receptor blocker (PD123,319, 4 micromol/L) blocked this effect. The Ang II-induced Ca(2+) increase was abolished by removal of extracellular Ca(2+) but not altered by depletion of intracellular Ca(2+) stores with thapsigargin. Ang II no longer elicited a Ca(2+) increase in the presence of lanthanum (25 micromol/L). The specific N-type and L-type Ca(2+) channel blockers, omega-conotoxin GVIA and nifedipine, respectively, significantly inhibited the Ang II-induced Ca(2+) increase. The protein kinase C inhibitor H7 but not the protein kinase A inhibitor H89 blocked the response to Ang II. These results demonstrate that Ang II selectively activates a subpopulation of postganglionic sympathetic neurons in aortic-renal and celiac ganglia, triggering Ca(2+) influx through voltage-gated Ca(2+) channels. This effect is mediated through AT(1) receptors and requires the activation of protein kinase C. The activation of a subgroup of sympathetic neurons by Ang II may exert unique effects on kidney function in pathological states associated with elevated Ang II.
血管紧张素II（Ang II）在麻醉小鼠中，无论神经节阻断前后均可增加肾交感神经活动，提示Ang II可能直接激活节后交感神经元。本研究在体外直接验证了这一假说。从C57BL/6J小鼠的主动脉-肾神经节和腹腔神经节中分离出神经元。使用fura 2通过比率成像测量细胞内钙离子浓度（Ca(2+)）。Ang II可使一部分交感神经元的Ca(2+)升高。在浓度为200 nmol/L时，21个神经元中有14个（67%）的Ca(2+)升高。血管紧张素II 1型（AT(1)）受体阻滞剂（氯沙坦，2 μmol/L）可阻断此效应，而血管紧张素II 2型（AT(2)）受体阻滞剂（PD123,319，4 μmol/L）则不能。去除细胞外钙离子可消除Ang II诱导的Ca(2+)升高，但用毒胡萝卜素耗尽细胞内钙库对此并无影响。在镧（25 μmol/L）存在的情况下，Ang II不再引起Ca(2+)升高。特异性的N型和L型钙离子通道阻滞剂，ω-芋螺毒素GVIA和硝苯地平，分别显著抑制了Ang II诱导的Ca(2+)升高。蛋白激酶C抑制剂H7可阻断对Ang II的反应，而蛋白激酶A抑制剂H89则不能。这些结果表明，Ang II可选择性激活主动脉-肾神经节和腹腔神经节中的一部分节后交感神经元，通过电压门控钙离子通道触发钙离子内流。此效应通过AT(1)受体介导，且需要蛋白激酶C的激活。在与Ang II升高相关的病理状态下，Ang II对一部分交感神经元的激活可能对肾功能产生独特影响。
