Zhu M, Gelband C H, Moore J M, Posner P, Sumners C
Department of Physiology, University of Florida, College of Medicine, Gainesville, Florida 32610, USA.
J Neurosci. 1998 Jan 15;18(2):679-86. doi: 10.1523/JNEUROSCI.18-02-00679.1998.
Angiotensin II (Ang II) elicits an Ang II type 2 (AT2) receptor-mediated increase in delayed-rectifier K+ current (IK) in neurons cultured from newborn rat hypothalamus and brainstem. This effect involves a pertussis toxin (PTX)-sensitive Gi protein and is abolished by inhibition of serine and threonine phosphatase 2A (PP-2A). Here, we determined that Ang II stimulates [3H]arachidonic acid (AA) release from cultured neurons via AT2 receptors. This effect of Ang II was blocked by inhibition of phospholipase A2 (PLA2) and by PTX. Because AA and its metabolites are powerful modulators of neuronal K+ currents, we investigated the involvement of PLA2 and AA in the AT2 receptor-mediated stimulation of IK by Ang II. Single-cell reverse transcriptase (RT)-PCR analyses revealed the presence of PLA2 mRNA in neurons that responded to Ang II with an increase in IK. The stimulation of neuronal IK by Ang II was attenuated by selective inhibitors of PLA2 and was mimicked by application of AA to neurons. Inhibition of lipoxygenase (LO) enzymes significantly reduced both Ang II- and AA-stimulated IK, and the 12-LO metabolite of AA 12S-hydroxyeicosatetraenoic acid (12S-HETE) stimulated IK. These data indicate the involvement of a PLA2, AA, and LO metabolite intracellular pathway in the AT2 receptor-mediated stimulation of neuronal IK by Ang II. Furthermore, the demonstration that inhibition of PP-2A abolished the stimulatory effects of Ang II, AA, and 12S-HETE on neuronal IK but did not alter Ang II-stimulated [3H]-AA release suggests that PP-2A is a distal event in this pathway.
血管紧张素II（Ang II）可引起新生大鼠下丘脑和脑干培养神经元中延迟整流钾电流（IK）的血管紧张素II 2型（AT2）受体介导的增加。这种效应涉及一种对百日咳毒素（PTX）敏感的Gi蛋白，并被丝氨酸和苏氨酸磷酸酶2A（PP - 2A）的抑制所消除。在此，我们确定Ang II通过AT2受体刺激培养神经元释放[3H]花生四烯酸（AA）。Ang II的这种效应被磷脂酶A2（PLA2）的抑制和PTX所阻断。由于AA及其代谢产物是神经元钾电流的强大调节剂，我们研究了PLA2和AA在Ang II介导的AT2受体对IK的刺激中的作用。单细胞逆转录酶（RT）-PCR分析显示，在对Ang II反应时IK增加的神经元中存在PLA2 mRNA。Ang II对神经元IK的刺激被PLA2的选择性抑制剂减弱，并被向神经元施加AA所模拟。脂氧合酶（LO）酶的抑制显著降低了Ang II和AA刺激的IK，并且AA的12-脂氧合酶代谢产物12S-羟基二十碳四烯酸（12S-HETE）刺激了IK。这些数据表明PLA2、AA和LO代谢产物的细胞内途径参与了Ang II介导的AT2受体对神经元IK的刺激。此外，PP-2A的抑制消除了Ang II、AA和12S-HETE对神经元IK的刺激作用，但不改变Ang II刺激的[3H]-AA释放，这表明PP-2A是该途径中的一个远端事件。
