Tanaka Satoru, Kanaya Noriaki, Homma Yasuyuki, Damron Derek S, Murray Paul A
Center for Anesthesiology Research FF40, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Anesthesiology. 2002 Dec;97(6):1557-66. doi: 10.1097/00000542-200212000-00031.
Vascular smooth muscle tone is regulated by changes in intracellular free Ca2+ concentration ([Ca2+]i) and myofilament Ca2+ sensitivity. These cellular mechanisms could serve as targets for anesthetic agents that alter vasomotor tone. This study tested the hypothesis that propofol increases myofilament Ca2+ sensitivity in pulmonary artery smooth muscle (PASM) via the protein kinase C (PKC) signaling pathway.
Canine PASM strips were denuded of endothelium, loaded with fura-2/AM, and suspended in modified Krebs-Ringer's buffer at 37 degrees C for simultaneous measurement of isometric tension and [Ca2+]i.
The KCl (30 mm) induced monotonic increases in [Ca2+]i and tension. Verapamil, an L-type Ca2+ channel blocker, attenuated KCl-induced increases in [Ca2+]i and tension to an equal extent. In contrast, propofol attenuated KCl-induced increases in [Ca2+]i to a greater extent than concomitant changes in tension and caused an upward shift in the peak tension-[Ca2+]i relation. Increasing extracellular Ca2+ in the presence of 30 mM KCl resulted in similar increases in [Ca2+]i in control and propofol-pretreated strips, whereas concomitant increases in tension were greater during propofol administration. The Ca2+ ionophore, ionomycin (0.1 microm), increased [Ca2+]i to approximately 50% of the value induced by 60 mm KCl. Under these conditions, propofol (10, 100 microm) caused increases in tension equivalent to 11 +/- 2 and 28 +/- 3% of the increases in tension in response to 60 mM KCl, whereas [Ca2+]i was slightly decreased. Similar effects were observed in response to the PKC activator, phorbol 12-myristate 13-acetate (PMA, 1 microm). Specific inhibition of PKC with bisindolylmaleimide I before ionomycin administration decreased the propofol- and PMA-induced increases in tension and abolished the propofol- and PMA-induced decreases in [Ca2+]i. Selective inhibition of Ca2+ -dependent PKC isoforms with Gö 6976 also attenuated propofol-induced increases in tension.
These results suggest that propofol increases myofilament Ca2+ sensitivity in PASM, and this effect involves the PKC signaling pathway.
血管平滑肌张力受细胞内游离钙离子浓度（[Ca2+]i）变化和肌丝对钙离子敏感性的调节。这些细胞机制可能成为改变血管运动张力的麻醉药物的作用靶点。本研究检验了丙泊酚通过蛋白激酶C（PKC）信号通路增加肺动脉平滑肌（PASM）肌丝对钙离子敏感性的假说。
去除犬PASM条带的内皮，用fura-2/AM负载，置于37℃的改良Krebs-Ringer缓冲液中，用于同时测量等长张力和[Ca2+]i。
氯化钾（30 mmol/L）使[Ca2+]i和张力呈单调增加。L型钙离子通道阻滞剂维拉帕米同等程度地减弱氯化钾诱导的[Ca2+]i和张力增加。相反，丙泊酚比张力的相应变化更大程度地减弱氯化钾诱导的[Ca2+]i增加，并使峰值张力-[Ca2+]i关系向上移位。在30 mmol/L氯化钾存在的情况下增加细胞外钙离子，对照条带和丙泊酚预处理条带中的[Ca2+]i增加相似，而丙泊酚给药期间张力的相应增加更大。钙离子载体离子霉素（0.1 μmol/L）使[Ca2+]i增加至60 mmol/L氯化钾诱导值的约50%。在这些条件下，丙泊酚（10、100 μmol/L）使张力增加相当于60 mmol/L氯化钾诱导张力增加的11±2%和28±3%，而[Ca2+]i略有下降。对PKC激活剂佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA，1 μmol/L）的反应也观察到类似效应。在给予离子霉素之前用双吲哚马来酰亚胺I特异性抑制PKC，可降低丙泊酚和PMA诱导的张力增加，并消除丙泊酚和PMA诱导的[Ca2+]i下降。用Gö 6976选择性抑制钙离子依赖性PKC同工型也减弱丙泊酚诱导的张力增加。
这些结果表明丙泊酚增加PASM的肌丝对钙离子敏感性，且该效应涉及PKC信号通路。
