胍丁胺抑制大鼠颈动脉窦压力感受器活动

在麻醉大鼠隔离灌流颈动脉窦区条件下,记录窦神经传入放电,观察胍丁胺（agmatine,Agm)对动脉压力感受器活动的影响,结果如下：（1）以1mmol/L Agm隔离灌流大鼠颈动脉窦区时,窦内压－窦神经传入放电积分（ISP－ISNA）关系曲线向右下方移位,曲线的最大斜率（PS）降低,窦神经传入放电量最大积分值（PIV）减小,再分别以5,10mmol/L Agm灌流时,机能曲线向右下方移位更为明显,PS及PIV降低更加明显,从而表明Agm抑制压力感受器活动且呈剂量依赖性,（2）α2－肾上腺素受体（α2－adrenoceptor,α-AR）和咪唑啉受体（IR）的阻断剂咪唑克生（0．1mmol/L)可阻断Agm的上述效应。（3）预先灌流α-AR能亨宾（15umol/L)可部分阻断Agm的抑制效应。（4）预先灌流Ca^2 通道激动剂Bay K8644(500mmol/L)亦可取消Agm对窦神经传入放电的影响,以上结果表明,Agm对基动脉窦压力感受器活动有抑制作用,此作用由IR和α-AR介导,并与颈动脉窦压力感受器活动时Ca^2 内流减少有关。     

白细胞介素-2引起离体大鼠主动脉环舒张及其作用机制

本文旨在研究白细胞介素－2（interleukin-2,IL-2）以离体大鼠胸主动脉环收缩张力的作用及其可能机制。采用累积加药法,检测IL－2对去氧肾上腺素（PE）和KCl预收缩的胸主动脉环收缩张力的影响。结果表明,IL－2（1、10、100、1000U／ml）对PE（10μmol/L）预收缩的内皮完整血管环产生浓度依赖性的舒张作用,而对KCl (120mmol/L）预收缩的血管无作用,去除内皮后,IL－2的舒张作用被取消。用一氧化氮合酶抑制剂L－NAME（0.1mmol/L）和鸟苷酸环化酶抑制剂亚甲蓝（10μmol/L）预处理,均可阻断IL－2的舒张血管作用。用环氧合酶抑制剂吲哚美辛（Indo,10μmol/L）预处理可阻断IL－2的血管舒张作用。从上述观察结果推论,IL－2通过NO－鸟苷酸环化酶和环氧合酶途径产生内皮依赖的血管舒张作用。     

NO在CCK—8减轻肿瘤坏死因子诱导兔肺动脉反应性变化中的作用

为探讨八肽胆囊收缩素（CCK－8）缓解内毒素休克时肺动脉高压的作用机制,应用离体血管环张力测定技术及一氧化氮合酶（NOS）检测方法,观察了一氧化氮（NO）在CCK－8减轻肿瘤坏死因子－α（tumor necrosis factor-al-pha,TNF-α）的抑制肺动脉内皮依赖性舒张反应中的作用。结果显示：TNF－α（4000U／ml）孵育2h时,肺动脉对10^-6mol/L苯肾上腺素(phenylephrine,PE）和10^-6mol/L乙酰胆碱（ACh）的收缩反应及内皮依赖性舒张反应均无明显变化。TNF－α孵育7或14h时,肺动脉对10^-6mol/L ACh介导的内皮依赖性舒张反应降低,CCK－8（0.5μg/ml）可逆转TNF－α的上述作用,CCK－8本身对正常肺动脉反应性无明显影响。TNF－α、CCK－8对PE引起的收缩反应无显著影响。L－精氨酸（L－Arg）可使TNF－α7h内皮依赖性舒张作用恢复。氨基胍（AG）不影响各组肺动脉对10^-6mol/L ACh的内皮依赖性舒张反应,而使TNF－α组肺动脉环对10^-6mol/L PE的收缩反应显著增加。L－硝基精氨酸（L－NNA）使各组肺动脉环对10^-6mol/L ACh反应由舒张变为收缩,对10^-6mol/L PE的收缩反应显著增强。检测7h各组NOS活性,TNF－α组、TNF－α＋CCK－8组均较对照组显著增加,CCK－8组与对照组比较无显著差异。上述结果提示,CCK－8可逆转TNF－α对内皮依赖性舒张反应的抑制作用,此作用可能与NO有关。     

双环醇减轻超氧阴离子诱导的大鼠胸主动脉舒张功能损伤

目的：探讨双环醇（bicyclol）对超氧阴离子（O2）诱导的血管舒张功能损伤的影响。方法：采用离体器官灌流技术,观察bicyclol对离体大鼠胸主动脉环张力的影响。采用焦酚（O2的供体）建立O2损伤模型,观察bicyclol预孵育对氧化应激损伤后血管内皮依赖性舒张功能的改善作用。结果：bicyclol（10-8~10-5mol/L）对由苯肾上腺素预收缩的内皮完整主动脉环产生舒张作用,该作用可被NO合酶抑制剂L-NAME和环氧化酶抑制剂吲哚美辛阻断。500μmol/L焦酚可引起乙酰胆碱诱导的主动脉环内皮依赖性舒张反应减弱,bicyclol（10-5mol/L）预孵育45 min可减轻焦酚的损伤作用。对于吲哚美辛处理的主动脉环,bicyclol（10-5mol/L）可抑制焦酚所致的血管舒张反应降低,但这一效应未见于L-NAME处理的主动脉环。结论：bicyclol具有内皮依赖性舒血管作用,并能对抗O2引起的血管舒张功能损伤,该作用通过NO途径介导。     

大、小动脉内皮细胞乙酰胆碱作用靶标药理学特性的比较

目的 :比较大、小动脉内皮细胞乙酰胆碱作用靶标药理学特性的差异。方法 :采用大鼠尾动脉螺旋状血管条和主动脉离体血管环两种组织 ,对比观察乙酰胆碱 (ACh)诱发大、小动脉内皮依赖性舒张反应特征的差异 ,从而进一步研究小动脉内皮细胞乙酰胆碱作用靶标的药理学特性。结果 :氯化钾 (6 0mmol/L)预致血管收缩的尾动脉和主动脉对不同浓度ACh (10 -8～ 10 -4mol/L)产生内皮依赖性舒张反应 ,且呈剂量依赖性。L Nω 硝基精氨酸甲酯 (L NAME :10 -4mol/L)或美蓝 (MB :10 -5mol/L)与吲哚美辛 (Indo :10 -4mol/L)联用仅可部分地阻断ACh诱发尾动脉内皮依赖性舒张反应 ;而L NAME或MB可完全阻断ACh诱发主动脉内皮依赖性舒张反应。结论 :ACh激活大、小动脉上内皮细胞乙酰胆碱作用靶标诱发内皮依赖性舒张反应的药理学性质不同 ,在小动脉上 ,除了NO和PGI2介导外 ,还有一种非NO和非PGI2 的舒血管因子参与 ;在大动脉上 ,内皮依赖性舒张反应主要由NO介导     

区域性血管床对局部注射胍丁胺的不同反应

在66只麻醉大鼠,分别采用后肢、肾脏和肠系膜动脉在体恒流灌注法,观察了向灌注环路中直接注射胍丁胺（agmatine,AGM）的血管效应,以所引起的灌流压增减反映血管的收缩和舒张。所得结果如下：（1）不同剂量的AGM（0.1、0.5、1mg/kg）注射于股部灌注环路时,可剂量依赖性地增高后肢血管的灌流压。无论预先注射咪唑啉受体(imidazoline receptor,IR）和α2－肾上腺素能受体阻断剂（α2－adrenergic receptor,α2－AR）idazoxan(0.5mg/kg）或注射α2-肾上腺素能受体阻断剂yohimbine(1mg/kg）均可完全阻抑上述AGM的效应。（2）向肾血管灌注环路中直接注射AGM也可剂量依赖性地增高肾血管的灌流压,需特别指出的是：大剂量AGM（1mg/mg）引起肾血管双相的灌注压增高,此效应可被idazoxan完全阻断。而在预先应用yohimbine后,再注射AGM则引起肾血管灌流压降低。（3）在肠系膜血管灌流环路中注射AGM可剂量依赖性地降低其灌流压。此效应可被idazoxan(0.5mg/kg）完全阻断,而yohimbine(1mg/kg）对此无作用。根据上述结果得出的结论是,AGM对后肢、肾脏和肠系膜血管床的血管紧张性具有不同的作用。     

α2—肾上腺素体介导大鼠主动脉收缩的特性

为阐明功能性α2－肾上腺素受体（α2－AR）的特性及其与α1－AR的相互关系,以离体大鼠主动脉为模型,进行收缩功能实验,发现在大鼠主动脉中,α1－AR和α2－AR产可介导其收缩效应并以α1－AR折作用为主,α1－AR可增强α2－AR介导的收缩效应,而α2－AR则对α1－AR介导的收缩效应无影响,在不可逆阻断α1－AR而保留α2－AR的条件下,α2－AR介导的缩血管效应消失,仅在阈值浓度的KCl存在下才能显示,且收缩幅度较对照组显著降低,结果表明,在离体大鼠主体动脉中存在功能性α2－AR,α2－AR的缩血管作用依赖于α1－AR的激动,其最大收缩反应远远小于α1－AR。     

白介素—2对心肌细胞[Ca^2＋]i的作用及其信号转导途径

为研究白介素－2（interleukin-2,IL-2）对心肌细胞内钙浓度（[Ca^2 ]i）的影响及其信号转导途径,实验采用酶解法分离成年大鼠心室肌细胞,以Fura-2/AM为钙探针,用细胞内双波长钙荧光系统检测细胞[Ca^2 ]i的变化。结果发现：（1）IL－2（0.5-200U/ml）浓度依赖性地降低单个心室肌细胞内钙态,IL－2（200U／ml）对咖啡因诱导的肌浆网内储钙的释放无影响;（2）纳洛酮(naloxone,Nal)(10^-8mol/L）和nor-binaltorphimine(nor-BNI,10^-8mol/L）可阻断IL－2对心肌细胞钙瞬态的作用,而纳曲吲哚（naltrindole,NTI）（10^-6mol/L）不能阻断此作用;（3）κ阿片受体激动剂U50488H（10^-6mol/L）降低心肌细胞钙瞬态,nor-BNI(10^-8mol/L）可阻断此作用;（4）5mg/L百日咳毒素（PTX）预处理可取消IL－2降低心肌细胞钙瞬态的作用,而酪氨酸激酶抑制剂genistein(10^-4mol/L）不能取消IL－2的作用;（5）U73122预处理可阻断IL－2的作用。研究结果表明,IL－2降低心肌细胞钙瞬态的作用,是通过心肌细胞上κ阿片受体介导的,其下游途径包括PTX敏感的G蛋白和磷脂酶C。     

美皂异黄酮非内皮依赖性血管舒张作用及其机制

目的:探讨植物雌激素美皂异黄酮舒张血管的可能机制。方法:采用MedLab生物信号采集系统记录灌流大鼠胸主动脉环张力变化。结果:美皂异黄酮(10-9~10-4mol/L)对苯肾上腺素(PE,10-5mol/L)预收缩的内皮完整或去内皮血管环均产生浓度依赖性的舒张作用;美皂异黄酮对高浓度氯化钾(KCl,6×10-2mol/L)预收缩的血管环也产生浓度依赖性的舒张作用;四乙胺(TEA,5×10-3mol/L)或格列苯脲(3×10-6mol/L)预处理对美皂异黄酮诱导的去内皮动脉环舒张作用具有明显的抑制效应;在无钙液中,美皂异黄酮抑制PE引起的去内皮主动脉环的短暂收缩。结论:美皂异黄酮的非内皮依赖性血管舒张作用的机制可能涉及血管平滑肌细胞的Ca2+激活K+通道和ATP敏感性K+通道的激活,以及肌浆网内钙离子释放的减少。     

淋巴细胞合成的内源性儿茶酚胺对T细胞增殖功能的影响

目的：提供淋巴细胞合成儿茶酚胺（CAs）的证据,并探讨淋巴细胞合成的内源性CAs对淋巴细胞自身功能的影响及其受体介导机制。方法：用RT-PCR技术检测CAs合成的限速酶酪氨酸羟化酶（TH）mRNA在大鼠肠系膜淋巴结细胞内的表达。用单胺氧化酶（CAs降解酶）的抑制剂优降宁及α1、α2、β1和β2肾上腺素受体（AR）的拮抗剂作用于淋巴细胞．然后用四唑蓝比色法测定淋巴细胞对刀豆蛋白A（ConA）刺激的增殖反应。结果：大鼠肠系膜淋巴结细胞具有,TH mRNA的表达,并且淋巴细胞在用ConA刺激活化后,其TH mRNA的表达明显上调。10^-6和10^-5mol／L优降宁能显著抑制ConA诱导的T淋巴细胞增殖,而10^-7mol／L优降宁不能明显降低T淋巴细胞的增殖反应。β2-AR拮抗剂ICI 118551（10^-7和10^-6mol／L）可完全阻断优降宁（10^-5mol／L）对T细胞增殖的抑制作用;α1-AR拮抗剂柯喃因和α2-AR拮抗剂育亨宾部分阻断优降宁抑制T细胞增殖的作用;而β1-AR拮抗剂阿替洛尔不能阻断优降宁的抑制作用。结论：淋巴细胞具有合成CAs的能力,这种合成能力随着淋巴细胞的激活而明显增强。淋巴细胞合成的内源性CAs可能通过自分泌或／和旁分泌路径主要激活淋巴细胞上的β2-AR,从而抑制T细胞的增殖反应。     

Relaxant effects of pravastatin, atorvastatin and cerivastatin on isolated rat aortic rings

Increasing evidence suggests that statins may have pleiotropic effects on vascular wall independent of their cholesterol lowering properties. In the present study, we investigated the acute vascular effects of pravastatin, atorvastatin and cerivastatin on rat isolated aortic rings. Statins effectively and comparably relaxed the aortic rings precontracted submaximally with noradrenaline, in a concentration-dependent manner, in which a high potency was observed with cerivastatin. Endothelium removal or incubation of the aortic rings with nitric oxide synthase inhibitor L-NOARG (10(-4) M) and/or cyclooxygenase inhibitor indomethacin (10(-5) M) significantly attenuated the acute vasorelaxation induced by either of statin. Additionally, different from the other two statins, a significant reduction was observed in response to cerivastatin in the presence of KATP channel inhibitor, glibenclamide (10(-5) M) and Na+- K+ ATPase inhibitor, ouabain (10(-4) M). Furthermore, pretreatment of the rings with the cholesterol precursor mevalonate (10(-3) M) significantly inhibited the endothelium-mediated relaxant effects of the statins. Our findings suggest that statins could acutely modulate vascular tone importantly by endothelium-dependent and mevalonate-related pathways.     

三羟异黄酮对离体家兔股动脉张力的影响及其机制

植物雌激素三羟异黄酮（genistein,GST)使离体的预先收缩的动脉舒张,其舒张的机制仍然不完全清楚。本研究旨在观察植物雌激素三羟异黄酮对离体家兔股动脉的作用及其机制,结果如下：（1）在苯肾上腺素（PE,1umol/L)引起血管收缩的基础上,GST（10－40umol/L)剂量依赖性地舒张离体家兔股动脉;（2）去除血管内皮显著地抑制GST引起的舒张;（3）在内皮完整情况下,预先应用NOS抑制剂L－NAME（100umol/L)也可显著地抑制GST引起的舒张,提示GST的舒血管作用是内皮依赖的,并与一氧化氮有关;（4）在内皮完整的扣去除内皮的股动脉环,预先应用L－型钙通道激动剂Bay M8644(0.5umol/L)也显著抑制由GST引起的血管舒张,以上结果表明,GST引起的兔股动脉的舒张是部分内皮依赖的,且与拮抗钙有关。     

Investigation of the vasorelaxant effects of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) and diethylamine/nitric oxide (DEA/NO) on the human radial artery used as coronary bypass graft

The radial artery (RA) is used as a spastic coronary bypass graft. This study was designed to investigate the mechanism of vasorelaxant effects of YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole), a nitric oxide (NO)-independent soluble guanylate cyclase (sGC) activator, and DEA/NO (diethylamine/nitric oxide), a NO-nucleophile adduct, on the human RA. RA segments (n = 25) were obtained from coronary artery bypass grafting patients and were divided into 3-4 mm vascular rings.Using the isolated tissue bath technique, the endothelium-independent vasodilatation function was tested in vitro by the addition of cumulative concentrations of YC-1 (10-10 to 3 x 10-7 mol/L) and DEA/NO (10-8 to 3 x 10-5 mol/L) following vasocontraction by phenylephrine in the presence or absence of 10-5 mol/L ODQ (1H-(1,2,4)oxadiazole(4,3-a)quinoxalin-1-one), the selective sGC inhibitor, 10-7 mol/L iberiotoxin, a blocker of Ca2+-activated K+ channels, or 10-5 mol/L ODQ plus 10-7 mol/L iberiotoxin. We also evaluated the effect of YC-1 and DEA/NO on the cGMP levels in vascular rings obtained from human radial artery (n = 6 for each drug). YC-1 (10-10 to 3 x 10-7 mol/L) and DEA/NO (10-8 to 3 x 10-5 mol/L) caused the concentration-dependent vasorelaxation in RA rings precontracted with phenylephrine (10-5 mol/L) (n = 20 for each drug). Pre-incubation of RA rings with ODQ, iberiotoxin, or ODQ plus iberiotoxin significantly inhibited the vasorelaxant effect of YC-1, but the inhibitor effect of ODQ plus iberiotoxin was significantly more than that of ODQ and iberiotoxin alone (p < 0.05). The vasorelaxant effect of DEA/NO almost completely abolished in the presence of ODQ and iberiotoxin plus ODQ, but did not significantly change in the presence of iberiotoxin alone (p > 0.05). The pEC50 value of DEA/NO was significantly lower than those for YC-1 (p < 0.01), with no change Emax values in RA rings. In addition, YC-1-stimulated RA rings showed more elevation in cGMP than that of DEA/NO (p < 0.05). These findings indicate that YC-1 is a more potent relaxant than DEA/NO in the human RA. The relaxant effects of YC-1 could be due to the stimulation of the sGC and Ca2+-sensitive K+channels, whereas the relaxant effects of DEA/NO could be completely due to the stimulation of the sGC. YC-1 and DEA/NO may be effective as vasodilator for the short-term treatment of perioperative spasm of coronary bypass grafts.     

Field stimulation-induced tetrodotoxin-resistant vasorelaxation is mediated by sodium hypochlorite

This study was done to determine the mechanism of field stimulation-induced tetrodotoxin (TTX)- and NG- nitro-l-arginine (LNA)-resistant vasorelaxation. Field stimulation with platinum and carbon, but not with silver, electrodes (30 V, 30 HZ, 2-5 ms pulse width) as well as electrically stimulated salt (0.9% NaCl) solution (ESSS) or Krebs solution caused 100% relaxation of phenylephrine-contracted rat aortic strips, which was TTX and LNA resistant and endothelium independent. ESSS also relaxed other vascular preparations (rabbit aorta and renal artery, dog coronary artery, pig ductus arteriosus, and rat portal vein). The electric current generated hypochlorite (OCl-) and H2O2 from the salt solution; however, vasorelaxation was caused by NaOCl and not by H2O2. ESSS and NaOCl caused contraction failure of spontaneously beating right atria of rats and did not affect uterine contractions, vascular cAMP, cGMP, or the pH of the tissue bath. Field stimulation, ESSS, and NaOCl did not relax aortic preparations contracted by 32 mmol/L potassium and their vasorelaxant effects on phenylephrine-contracted rat aortic strips and rings were completely reversed by tetraethylammonium and partially by glibenclamide and iberiotoxin. We conclude that electric pulses generate the oxidant OCl- from the salt solution, which causes vasorelaxation by increasing K+ conductance.     

Characterization of the vasorelaxation to methanandamide in rat gastric arteries

In the present study, the relaxant effect of the cannabinoid methanandamide was explored in rat gastric arteries. Since in some vessels cannabinoids have been shown to release calcitonin gene-related peptide (CGRP) from perivascular nerves, the influence of methanandamide was compared with that of exogenous CGRP. Methanandamide and CGRP elicited concentration-dependent, endothelium-independent relaxations. Methanandamide-induced relaxations were unaffected by the CB1 receptor antagonist AM251, the CB2 receptor antagonists AM630 and SR144528, and combined pre-exposure to AM251 and SR144528. Pre-exposure to O-1918, an antagonist of a novel nonCB1/nonCB2 cannabinoid receptor, did not influence the relaxations to methanandamide. Capsaicin or capsazepine treatment slightly inhibited methanandamide-induced relaxations. Preincubation with 30 mmol/L extracellular K+ or 3 mmol/L TEA had no significant effect on the responses elicited by methanandamide, but reduced CGRP-induced relaxations. Relaxation to 10(-5) mol/L methanandamide was significantly blunted by Bay K8644 and by preincubation with nifedipine. Furthermore, 10(-5) mol/L methanandamide significantly inhibited CaCl2-induced contractions in norepinephrine-stimulated vessels previously depleted of intra- and extracellular Ca2+. Finally, preincubation with 10(-5) mol/L methanandamide almost completely abolished high K+-induced contractions. These findings suggest that the vasorelaxant action of methanandamide in rat gastric arteries is not mediated by stimulation of known cannabinoid receptors and only partly related to stimulation of TRPV1 receptors on perivascular nerves. At high concentrations, methanandamide might induce relaxation by reducing calcium entry into the smooth muscle cells.     

Anandamide-induced vasorelaxation in rabbit aortic rings has two components: G protein dependent and independent

The endogenous cannabinoid anandamide (arachidonylethanolamide) produces vasorelaxation in different vascular beds. In the present study, we found that anandamide and a metabolically stable analog, methanandamide, produced dose-dependent (10 nM-10 microM) vasorelaxation of approximately 80% in a rabbit aortic ring preparation in an endothelium-dependent manner. Non-endothelium-dependent vasorelaxation was observed to be a maximum of 20-22% at >10 microM methanandamide. The efficacious CB(1) receptor analogs desacetyllevonantradol (10 microM) and WIN55212-2 (10 microM) failed to produce vasorelaxation; however, the endothelium-dependent vasorelaxation evoked by methanandamide was partially (75%) blocked by the CB(1) receptor antagonist SR141716A. The VR(1) vanilloid receptor antagonist capsazepine or the calcitonin gene-related peptide (CGRP) antagonist CGRP-(8-37) partially attenuated (25%) the vasorelaxation in endothelium-intact preparations and greatly reduced the response in endothelium-denuded preparations. Pretreatment of aortic rings with N(G)-nitro-L-arginine methyl ester completely blocked the methanandamide-, capsaicin-, and CGRP-induced vasorelaxation. Pretreatment of aortic rings with pertussis toxin attenuated the methanandamide-induced vasorelaxation in endothelium-intact aortic rings, indicating the involvement of G(i/o) proteins in the vasorelaxation; however, pertussis toxin treatment failed to block the endothelium-independent response. Thus, in the rabbit aorta, methanandamide-induced vasorelaxation exhibits two components: 1) in endothelium-intact rings, an SR141716A-sensitive, non-CB(1) receptor component that requires pertussis toxin-sensitive G proteins and nitric oxide (NO) production; and 2) in endothelium-denuded rings, a component that is mediated by VR(1) vanilloid receptors and possibly by the subsequent release of CGRP that requires NO production but is independent of pertussis toxin-sensitive G proteins.     

Tyrosine kinases regulate intracellular calcium during alpha(2)-adrenergic contraction in rat aorta

We have demonstrated enhanced contractile sensitivity to the alpha(2)-adrenoreceptor (alpha(2)-AR) agonist UK-14304 in arteries from rats made hypertensive with chronic nitric oxide synthase (NOS) inhibition (LHR) compared with arteries from normotensive rats (NR); additionally, this contraction requires Ca(2+) entry. We hypothesized that tyrosine kinases augment alpha(2)-AR contraction in LHR arteries by increasing Ca(2+). The tyrosine kinase inhibitor tyrphostin 23 significantly attenuated UK-14304 contraction of denuded thoracic aortic rings from NR and LHR. However, tyrphostin 23 did not alter UK-14304 contraction in ionomycin-permeabilized aorta, which indicates that tyrosine kinases regulate intracellular Ca(2+) concentration. The Src family inhibitor PP1 and the epidermal growth factor receptor kinase inhibitor AG-1478 did not alter alpha(2)-AR contraction, whereas the mitogen-activated protein kinase extracellular signal-regulated kinase kinase inhibitor PD-98059 attenuated the contraction. Contraction to CaCl(2) in ionomycin-permeabilized LHR rings was greater than in NR rings. UK-14304 augmented CaCl(2) contraction in ionomycin-permeabilized rings from both groups but to a greater extent in LHR aorta. Together, these data suggest that alpha(2)-AR stimulates contraction via two pathways. One, which is enhanced with NOS inhibition hypertension, activates Ca(2+) sensitivity and is independent of tyrosine kinases. The other is tyrosine kinase dependent and regulates intracellular Ca(2+) concentration.     

Mechanism of enhanced calcium sensitivity and alpha 2-AR vasoreactivity in chronic NOS inhibition hypertension

PKC augments calcium sensitivity in spontaneously hypertensive rats and contributes to alpha(2)-adrenergic receptor (AR) contraction in rabbit saphenous vein. We showed previously that denuded aortic rings from N(omega)-nitro-l-arginine-treated hypertensive rats (LHR) contract more to CaCl(2) and to the alpha(2)-AR agonist UK-14304 than do rings from normotensive rats (NR). We hypothesized that enhanced PKC activity or a change in PKC isoform contributes to augmented calcium sensitivity and enhanced alpha(2)-AR contraction in LHR aorta. Current studies demonstrate that non-isoform-specific PKC inhibitors reduced UK-14304 contraction in both NR and LHR aorta. However, the calcium-dependent PKC inhibitor G?-6976 only attenuated contraction in LHR aorta. Additionally, UK-14304 translocated PKC-delta to the membrane in NR aorta, whereas PKC-alpha was translocated to the membrane in LHR aorta. Finally, in ionomycin-permeabilized aorta G?-6976 eliminated enhanced basal and augmented alpha(2)-AR-stimulated calcium sensitivity in LHR aorta but did not affect NR contraction. Together, these data suggest that PKC-alpha contributes to augmented calcium sensitivity and alpha(2)-AR reactivity after chronic nitric oxide synthase inhibition hypertension.