Mechanism of inhibition of tubuloglomerular feedback by CO and cGMP.
Mechanism of inhibition of tubuloglomerular feedback by CO and cGMP.
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DOI：
10.1161/hypertensionaha.113.01164
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发表时间：
2013-07
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影响因子：
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通讯作者：
Carretero OA
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作者：
Ren Y;D'Ambrosio MA;Garvin JL;Wang H;Carretero OA
肾小管肾小球反馈（TGF）是一种在致密斑（MD）中感知NaCl并引起传入小动脉收缩（Af-Art）的机制。内源性或外源性的一氧化碳（CO）至少部分地通过cGMP抑制TGF。我们假设，CO在MD，通过cGMP依赖性和非依赖性机制，减弱TGF-β的下游去极化和钙进入MD细胞。在体外，显微解剖的兔Af-Arts和它们的MD同时灌注，并且测量TGF作为Af-Arts直径的减小。MD去极化诱导离子载体，同时添加CO释放分子CORM-3的MD灌注液在无毒浓度。CORM-3使TGF诱导的去极化在50 μM时从3.6±0.4 μm减弱到2.5±0.4 μm（P<0.01），在100 μM时消除到0.1±0.1 μm（P<0.001，n=6）。在MD中加入鸟苷酸环化酶抑制剂LY-83583阻断cGMP生成后，CORM-3在50 μM浓度下不再影响去极化诱导的TGF（2.9±0.4 vs.3.0 ±0.4 μm），但在100 μM浓度下部分抑制TGF（至1.3±0.2 μm，P<0.05，n=9）。使用ETYA和吲哚美辛的实验表明，花生四烯酸代谢产物不介导CO的cGMP非依赖性作用。CORM-3在50 μM（1.9±0.6 μ M，P<0.01）和100 μM（0.2±0.5 μM，P <0.001，n=6）时抑制A23187诱导的TGF β。我们的结论是，CO抑制TGF-β作用下游的去极化和钙离子进入，通过cGMP在低浓度下发挥作用，但其他机制的行动可能涉及在较高的浓度。
Tubuloglomerular feedback (TGF) is a mechanism that senses NaCl in the macula densa (MD) and causes constriction of the afferent arteriole (Af-Art). Carbon monoxide (CO), either endogenous or exogenous, inhibits TGF at least in part via cGMP. We hypothesize that CO in the MD, acting via both cGMP-dependent and - independent mechanisms, attenuates TGF by acting downstream from depolarization and Ca entry into the MD cells. In vitro, microdissected rabbit Af-Arts and their MD were simultaneously perfused and TGF was measured as the decrease in Af-Art diameter. MD depolarization was induced with ionophores, while adding the CO-releasing molecule CORM-3 to the MD perfusate at non-toxic concentrations. CORM-3 blunted depolarization-induced TGF at 50 μM, from 3.6±0.4 to 2.5±0.4 μm (P<0.01), and abolished it at 100 μM, to 0.1±0.1 μm (P<0.001, n=6). When cGMP generation was blocked by guanylyl cyclase inhibitor LY-83583 added to the MD, CORM-3 no longer affected depolarization-induced TGF at 50 μM (2.9±0.4 vs. 3.0±0.4 μm), but partially inhibited TGF at 100 μM (to 1.3±0.2 μm, P<0.05, n=9). Experiments using ETYA and indomethacin suggest arachidonic acid metabolites do not mediate the cGMP-independent effect of CO. We then added the calcium ionophore A23187 to the macula densa, which caused TGF (4.1±0.6 μM); A23187-induced TGF was inhibited by CORM-3 at 50 μM (1.9±0.6 μM, P<0.01) and 100 μM (0.2±0.5 μM, P<0.001, n=6). We conclude that CO inhibits TGF acting downstream from depolarization and calcium entry, acting via cGMP at low concentrations, but additional mechanisms of action may be involved at higher concentrations.