Characterization and modulation of EDHF‐mediated relaxations in the rat isolated superior mesenteric arterial bed
Characterization and modulation of EDHF‐mediated relaxations in the rat isolated superior mesenteric arterial bed
复制标题
大鼠离体肠系膜上动脉床 EDHF 介导的舒张的表征和调节
DOI：
--
复制
发表时间：
1997
影响因子：
7.3
通讯作者：
C. Robin Hiley
中科院分区：
文献类型：
--
作者：
A. Mcculloch;F. Bottrill;M. Randall;C. Robin Hiley
我们使用分离的，缓冲灌注的，大鼠的系膜动脉床（用甲氧苄胺或60 mm K+预收缩）来表征一氧化氮（NO）独立的血管松弛，这被认为是由内皮衍生的超极化因子（EDHF）介导的。毒毒碱激动剂甲胆碱、乙酰胆碱和甲胆碱在预缩制剂中引起剂量相关性松弛，ED50值分别为0.18±0.04 nmol （n=8）、0.05±0.02 nmol （n=6）和0.26±0.16 nmol （n=5）。在相同的制剂中，NG -硝基- l -精氨酸甲酯（l - NAME, 100 μm）显著（P<0.05）降低了所有药物的效力（l - NAME存在时的ED50值：氨基苯酚，0.66±0.11 nmol; ACh, 0.28±0.10 nmol；甲胆碱，1.97±1.01 nmol）。l‐NAME存在时，对ACh的最大弛豫也显著（P<0.05）降低（从85.3±0.9降至73.2±3.7%）。环氧合酶抑制剂吲哚美辛（10 μm; n=4）未显著改变卡巴吉醇的血管松弛作用。K+通道阻滞剂四乙基铵（TEA, 10 mm）也显著（P<0.001）降低了氨基苯酚的效价（TEA存在时ED50=1.97±0.14 nmol）和最大弛豫（TEA存在时Rmax=74.6±3.2%，P<0.05, n=3）。在l‐NAME存在的情况下添加TEA (n=4)，与l‐NAME单独存在时相比，carbachol的效价（ED50=22.4±13.5 nmol）进一步显著降低（P<0.001）， Rmax也显著降低（P<0.05）（74.6±4.2%）。ATP敏感的K+通道抑制剂格列本脲（10 μm）对碳乙醇诱导的松弛没有影响（n=9）。高K+ (60 mm)显著（P<0.01）降低了5倍（ED50：对照组，0.16±0.04 nmol；高K+， 0.88±0.25 nmol）， Rmax也显著（P<0.01）降低（对照组，83.4±2.7%；高K+， 40.3±9.2%）。l‐NAME （100 μm; n=5）消除了高K+存在下残留的血管松弛。在高K+预缩制剂中，硝普钠的效价与甲氧胺预缩制剂无显著差异，但最大反应降低（高K+ 62.4±3.4%,n=7；对照83.1±3.1%,n=7）。细胞色素P450抑制剂clotrimazole （1 μm, n=5和10 μm， n=4）存在时，对carbachol的剂量响应曲线分别显著右移2倍（P<0.05）和4倍（P<0.001）， l‐NAME存在时，这种效应进一步增强。单独存在10 μm氯霉唑显著降低Rmax (P<0.01)，不存在时为86.9±2.5%，存在时为61.8±7.8% （n=6）。当细胞可渗透的环GMP类似物8 -溴环GMP （6 μm）存在时，l - NAME对碳酒酚诱导的松弛的抑制作用显著增强（ED50: l - NAME单独，0.52±0.11 nmol, n=5； l - NAME+8 -溴环GMP， 1.42±0.28 nmol, n=7）。Rmax: l‐NAME单独，82.2±2.4%；l‐NAME+8‐溴环GMP， 59.1±1.8%。P < 0.001)。这些结果表明，当维持功能性环GMP水平时，血管舒张中NO独立成分的强度降低，这表明基础NO（通过环GMP）可能调节EDHF活性，因此，在基础NO产生减少的情况下，内皮依赖性舒张中的EDHF成分在功能上变得更大。本研究表明，毒蕈碱受体诱导的大鼠肠系膜动脉床血管松弛是由一氧化氮依赖性和独立机制介导的。l - NAME -不敏感机制，最有可能通过激活K+电导发生，并显示EDHF介导反应的特征。最后，研究结果表明，EDHF活性可能会因抑制NO的产生而上调，这可能会弥补NO的损失。
We have used the isolated, buffer‐perfused, mesenteric arterial bed of the rat (preconstricted with methoxamine or 60 mm K+) to characterize nitric oxide (NO)‐independent vasorelaxation which is thought to be mediated by the endothelium‐derived hyperpolarizing factor (EDHF). The muscarinic agonists carbachol, acetylcholine (ACh) and methacholine caused dose‐related relaxations in preconstricted preparations with ED50 values of 0.18±0.04 nmol (n=8), 0.05±0.02 nmol (n=6) and 0.26±0.16 nmol (n=5), respectively. In the same preparations NG‐nitro‐l‐arginine methyl ester (l‐NAME, 100 μm) significantly (P<0.05) decreased the potency of all the agents (ED50 values in the presence of l‐NAME: carbachol, 0.66±0.11 nmol; ACh, 0.28±0.10 nmol; methacholine, 1.97±1.01 nmol). The maximal relaxation to ACh was also significantly (P<0.05) reduced (from 85.3±0.9 to 73.2±3.7%) in the presence of l‐NAME. The vasorelaxant effects of carbachol were not significantly altered by the cyclo‐oxygenase inhibitor indomethacin (10 μm; n=4). The K+ channel blocker, tetraethylammonium (TEA, 10 mm) also significantly (P<0.001) reduced both the potency of carbachol (ED50=1.97±0.14 nmol in presence of TEA) and the maximum relaxation (Rmax=74.6±3.2% in presence of TEA, P<0.05, n=3). When TEA was added in the presence of l‐NAME (n=4), there was a further significant (P<0.001) decrease in the potency of carbachol (ED50=22.4±13.5 nmol) relative to that in the presence of l‐NAME alone, and Rmax was also significantly (P<0.05) reduced (74.6±4.2%). The ATP‐sensitive K+ channel inhibitor, glibenclamide (10 μm), had no effect on carbachol‐induced relaxation (n=9). High extracellular K+ (60 mm) significantly (P<0.01) reduced the potency of carbachol (n=5) by 5 fold (ED50: control, 0.16±0.04 nmol; high K+, 0.88±0.25 nmol) and the Rmax was also significantly (P<0.01) reduced (control, 83.4±2.7%; high K+, 40.3±9.2%). The residual vasorelaxation to carbachol in the presence of high K+ was abolished by l‐NAME (100 μm; n=5). In preparations preconstricted with high K+, the potency of sodium nitroprusside was not significantly different from that in preparations precontracted with methoxamine, though the maximal response was reduced (62.4±3.4% high K+, n=7; 83.1±3.1% control, n=7). In the presence of the cytochrome P450 inhibitor, clotrimazole (1 μm, n=5 and 10 μm, n=4), the dose‐response curve to carbachol was significantly shifted to the right 2 fold (P<0.05) and 4 fold (P<0.001) respectively, an effect which was further enhanced in the presence of l‐NAME. Rmax was significantly (P<0.01) reduced by the presence of 10 μm clotrimazole alone, being 86.9±2.5% in its absence and 61.8±7.8% in its presence (n=6). In the presence of the cell permeable analogue of cyclic GMP, 8‐bromo cyclic GMP (6 μm), the inhibitory effects of l‐NAME on carbachol‐induced relaxation were substantially enhanced (ED50: l‐NAME alone, 0.52±0.11 nmol, n=5; l‐NAME+8‐bromo cyclic GMP, 1.42±0.28 nmol, n=7. Rmax: l‐NAME alone, 82.2±2.4%; l‐NAME+8‐bromo cyclic GMP, 59.1±1.8%. P<0.001). These results suggest that the magnitude of the NO‐independent component of vasorelaxation is reduced when functional cyclic GMP levels are maintained, suggesting that basal NO (via cyclic GMP) may modulate EDHF activity and, therefore, on loss of basal NO production the EDHF component of endothelium‐dependent relaxations becomes functionally greater. The present investigation demonstrates that muscaranic receptor‐induced vasorelaxation in the rat mesenteric arterial bed is mediated by both NO‐dependent and independent mechanisms. The l‐NAME‐insensitive mechanism, most probably occurs via activation of a K+ conductance and shows the characteristics of EDHF‐mediated responses. Finally, the results demonstrate that EDHF activity may become upregulated on inhibition of NO production and this may compensate for the loss of NO.
登录
查看更多内容
DOI：
--
发表时间：
1991-09
期刊：
The Journal of pharmacology and experimental therapeutics
影响因子：
--
作者：
N. Jaiswal;G. Lambrecht;E. Mutschler;R. Tacke;K. Malik
通讯作者：
N. Jaiswal;G. Lambrecht;E. Mutschler;R. Tacke;K. Malik
影响因子：
20.1
作者：
Campbell, WB;Gebremedhin, D;Harder, DR
通讯作者：
Harder, DR
钾诱导犬股动脉释放内皮源性舒张因子。
影响因子：
20.1
作者：
Rubanyi,GM;Vanhoutte,PM
通讯作者：
Vanhoutte,PM
DOI：
--
发表时间：
1993
期刊：
The Journal of pharmacology and experimental therapeutics
影响因子：
--
作者：
Cowan,CL;Palacino,JJ;Najibi,S;Cohen,RA
通讯作者：
Cohen,RA