Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, United States of America.
PLoS One. 2013 Dec 4;8(12):e82482. doi: 10.1371/journal.pone.0082482. eCollection 2013.
The present study examined whether 20-hydroxyeicosatetraenoic acid (HETE) contributes to the vasoconstrictor effect of angiotensin II (ANG II) in renal microvessels by preventing activation of the large conductance Ca(2+)-activated K(+) channel (KCa) in vascular smooth muscle (VSM) cells. ANG II increased the production of 20-HETE in rat renal microvessels. This response was attenuated by the 20-HETE synthesis inhibitors, 17-ODYA and HET0016, a phospholipase A2 inhibitor AACOF3, and the AT1 receptor blocker, Losartan, but not by the AT2 receptor blocker, PD123319. ANG II (10(-11) to 10(-6) M) dose-dependently decreased the diameter of renal microvessels by 41 ± 5%. This effect was blocked by 17-ODYA. ANG II (10(-7) M) did not alter KCa channel activity recorded from cell-attached patches on renal VSM cells under control conditions. However, it did reduce the NPo of the KCa channel by 93.4 ± 3.1% after the channels were activated by increasing intracellular calcium levels with ionomycin. The inhibitory effect of ANG II on KCa channel activity in the presence of ionomycin was attenuated by 17-ODYA, AACOF3, and the phospholipase C (PLC) inhibitor U-73122. ANG II induced a peak followed by a steady-state increase in intracellular calcium concentration in renal VSM cells. 17-ODYA (10(-5) M) had no effect on the peak response, but it blocked the steady-state increase. These results indicate that ANG II stimulates the formation of 20-HETE in rat renal microvessels via the AT1 receptor activation and that 20-HETE contributes to the vasoconstrictor response to ANG II by blocking activation of KCa channel and facilitating calcium entry.
本研究探讨了 20-羟二十碳四烯酸 (HETE) 是否通过防止血管平滑肌 (VSM) 细胞中大电导钙激活钾 (KCa) 通道的激活，从而导致血管紧张素 II (ANG II) 在肾微血管中的血管收缩作用。ANG II 增加了大鼠肾微血管中 20-HETE 的产生。这种反应被 20-HETE 合成抑制剂 17-ODYA 和 HET0016、磷脂酶 A2 抑制剂 AACOF3 和 AT1 受体阻滞剂 Losartan 减弱，但不受 AT2 受体阻滞剂 PD123319 的影响。ANG II（10(-11) 至 10(-6) M）剂量依赖性地使肾微血管直径缩小 41 ± 5%。这种作用被 17-ODYA 阻断。ANG II（10(-7) M）在对照条件下不会改变细胞附着在肾 VSM 细胞上的贴附斑上的 KCa 通道活性。然而，当用离子霉素增加细胞内钙水平激活通道时，ANG II 确实将 KCa 通道的 NPo 减少了 93.4 ± 3.1%。在存在离子霉素的情况下，17-ODYA、AACOF3 和 PLC 抑制剂 U-73122 减弱了 ANG II 对 KCa 通道活性的抑制作用。ANG II 在肾 VSM 细胞中诱导钙内流的峰后稳态增加。17-ODYA（10(-5) M）对峰反应没有影响，但阻断了稳态增加。这些结果表明，ANG II 通过 AT1 受体的激活刺激大鼠肾微血管中 20-HETE 的形成，并且 20-HETE 通过阻断 KCa 通道的激活和促进钙内流，有助于对 ANG II 的血管收缩反应。
