Ca2+-independent hypoxic vasorelaxation in porcine coronary artery.
Ca2+-independent hypoxic vasorelaxation in porcine coronary artery.
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猪冠状动脉中Ca2+独立的缺氧血管舒张作用。
DOI：
10.1113/jphysiol.2004.073692
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Paul,RichardJ
中科院分区：
文献类型：
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作者：
Gu,Min;Thorne,GeorgeD;Wardle,RobertL;Ishida,Yukisato;Paul,RichardJ
为了证明缺氧性血管舒张的Ca 2+非依赖性成分并研究其机制，我们使用了透化的猪冠状动脉，其中[Ca 2 +]可以被夹紧。用β-七叶皂苷透化的动脉对游离Ca 2+（6.6 μm）产生最大反应力，同时肌球蛋白调节轻链磷酸化（MRLC-Pi）平行增加，从0.183 ± 0.023增加到0.353 ± 0.019 MRLC-Pi（总轻链）−1。尽管EGTA（4 mm）缓冲了恒定的[Ca 2 +]，但缺氧仍导致力（产生力之前的-31.9 ± 4.1%）和MRLC-Pi（从0.353降至0.280 ± 0.023）显着下降。Ca ~（2+）（6.6 μm）、Ca ~（2+）（0.2 μm）+ GTPγS（1 mm）或无Ca ~（2+）条件下ATPγS（1 mm）处理后产生的力大小相似。缺氧也可使GTPγS挛缩松弛，但重要的是，ATPγS处理后不能使动脉松弛。Triton X-100透化60分钟也消除了缺氧松弛。ATPγS后缺氧松弛的阻断表明，这种Ca 2+非依赖性机制可能通过改变肌球蛋白轻链磷酸酶肌球蛋白结合亚基磷酸化的MRLC-Pior来发挥作用。用Rho激酶抑制剂Y27632（1 μm）处理可松弛GTPγS和Ca 2+挛缩;但后者需要更高的浓度（10 μm）才能持续松弛。对N2和/或Y27632的弛豫平均为35%，并且不加和或依赖于顺序。我们的数据表明，GTP介导的Rho激酶偶联途径值得进一步研究，作为这种新型的Ca 2+非依赖性O2-传感机制的潜在位点。重要的是，这些结果明确表明，缺氧诱导的血管舒张可发生在Ca 2+被钳制在恒定值的透化动脉中。
To demonstrate a Ca2+‐independent component of hypoxic vasorelaxation and to investigate its mechanism, we utilized permeabilized porcine coronary arteries, in which [Ca2+] could be clamped. Arteries permeabilized with β‐escin developed maximum force in response to free Ca2+(6.6 μm), concomitant with a parallel increase in myosin regulatory light chain phosphorylation (MRLC‐Pi), from 0.183 ± 0.023 to 0.353 ± 0.019 MRLC‐Pi(total light chain)−1. Hypoxia resulted in a significant decrease in both force (–31.9 ± 4.1% prior developed force) and MRLC‐Pi(from 0.353 to 0.280 ± 0.023), despite constant [Ca2+] buffered by EGTA (4 mm). Forces developed in response to Ca2+(6.6 μm), Ca2+(0.2 μm) + GTPγS (1 mm), or in the absence of Ca2+after treatment with ATPγS (1 mm), were of similar magnitude. Hypoxia also relaxed GTPγS contractures but importantly, arteries could not be relaxed after treatment with ATPγS. Permeabilization with Triton X‐100 for 60 min also abolished hypoxic relaxation. The blocking of hypoxic relaxation after ATPγS suggests that this Ca2+‐independent mechanism(s) may operate through alteration of MRLC‐Pior of phosphorylation of the myosin binding subunit of myosin light chain phosphatase. Treatment with the Rho kinase inhibitor Y27632 (1 μm) relaxed GTPγS and Ca2+contractures; but the latter required a higher concentration (10 μm) for consistent relaxation. Relaxations to N2and/or Y27632 averaged 35% and were not additive or dependent on order. Our data suggest that the GTP‐mediated, Rho kinase‐coupled pathway merits further investigation as a potential site of this novel, Ca2+‐independent O2‐sensing mechanism. Importantly, these results unambiguously show that hypoxia‐induced vasorelaxation can occur in permeabilized arteries where the Ca2+is clamped at a constant value.