L-arg和LNNA对大鼠胸主动脉内皮损伤后舒缩反应及cGMP含量的影响

本研究在大鼠胸主动脉内皮损伤内膜增生模型上观察了Ｌ－ａｒｇ和ＬＮＮＡ对大鼠胸主动脉条的血管反应性及ｃＧＭＰ含量的影响。血管反应性观察及血管局部ｃＧＭＰ测定发现,大鼠胸主动脉内皮损伤后３天对－ａｒｇ及ＬＮＮＡ的舒缩反应明显受损,血管局部基础ｃＧＭＰ明显下降,用Ｌ－ａｒｇ和ＬＮＮＡ干预后的ｃＧＭＰ变化亦明显受损,损伤后１０天,以上现象明显恢复,损伤后２１天进一步恢复,但仍不能恢复正常。结果表明,内皮损伤后的动脉血管ＥＤＲＦ产生明显受损,且长期不能恢复正常。     

内皮源性舒张因子对内皮损伤的大鼠胸主动脉中血管紧张素Ⅱ的影响

利用放免测定法在大鼠胸主动脉内皮损伤内膜增生模型上观察了内皮源性舒张因子（ＥＤＲＦ）的前体Ｌ－Ａｒｇ和抑制剂ＬＮＮＡ对内皮损伤血管局部ｃＧＭＰ（ＥＤＲＦ的效应物）和Ａｇ－Ⅱ水平的影响。结果发现,动脉血管内皮损伤后,其ｃＧＭＰ含量显著下降,血管局部Ａｇ－Ⅱ水平明显上升;ＬＮＮＡ可使这一现象更加明显;而Ｌ－Ａｒｇ却可使内皮损伤动脉中下降的ｃＧＭＰ明显上升,使其升高的局部Ａｇ－Ⅱ水平明显下降。表明ＥＤＲＦ可通过ｃＧＭＰ途径抑制内皮损伤的动脉中Ａｇ－Ⅱ的产生。     

NO—样松弛因子对止血带休克大鼠血管舒缩活动的影响

本工作在大鼠止血带休克（ＴｏＳ）模型上观察ＮＯ前体Ｌ－精氨酸Ｌ－Ａｒｇ,ＮＯ合成阻断剂Ｌ－ＮＮＡ及可溶性鸟苷酸环化酶抑制剂亚甲兰（ＭＢ）对离体胸主动脉舒缩活动的影响。发现止血带休克大鼠离体灌流的主动脉对去甲肾上腺素的反应性降低。血管组织ｃＧＭＰ含量增加。Ｌ－Ａｒｇ可增强这一变化,而Ｌ－ＮＮＡ或ＭＢ可减轻上述变化,而且这些药物作用不受血管内皮是否存在的影响。实验结果提示,非内皮细胞源的ＮＯ－样松弛因子（ＮＯ－ＬＲＦ）是引起止血带休克动物血管低反应性的因素之一     

肾上腺髓质素（13－52）降压机制的探讨

本工作在整体和离体大鼠模型上观察研究了肾上腺髓质素（１３－５２）［ＡｄＭ（１３－５２）］的降压机制,发现ＡｄＭ（１３－５２）的降压作用可被一氧化氮合酶（ＮＯＳ）的竟争性桔抗剂Ｌ－ＮＧ－硝基－精氨酸（ＬＮＮＡ）部分抑制;ＡｄＭ（１３－５２）的舒血管作用依赖于血管内皮并可被ＬＮＮＡ抑制,且具有剂量效应关系,ＬＮＮＡ的这种效应可被Ｌ－精氨酸（Ｌ－Ａｒｇ）逆转;用亚甲蓝（ＭＢ）阻断血管内的环－磷酸鸟苷酸（ｃＧＭＰ）,则导致ＡｄＭ（１３－５２）的舒血管作用消失;放免测定显示ＬＮＮＡ可以降低血管内ｃＧＭＰ含量,而ＡｄＭ（１３－５２）则使后者含量增加,这一现象在ＡｄＭ（１３－５２）与ＬＮＮＡ合用时消失。实验结果提示,ＡｄＭ（１３－５２）的舒血管降血压效应与ＮＯ有关,可能是通过ＮＯ介导的。     

肾上腺髓质素（13—52）降压机制的探讨

本工作在整体和离体大鼠模型上观察肾上腺髓质素（１３－５２）［ＡｄＭ（１３－５２）］的降压机制,发现ＡｄＭ（１３－５２）的降压作用可被一氧化氮合酶（ＮＯＳ）竞争性拮抗剂Ｌ－Ｎ－硝基－精氨酸？（ＬＮＮＡ）部分抑制;ＡｄＭ１３－５２）的舒血管作用依赖于血管内皮并可被ＬＮＮＡ抑制,且具有剂量效应,ＬＮＮＡ这种效应可被Ｌ－精氨酸（ＬＡｒｇ）逆转;用亚甲蓝（ＭＢ）阻断血管内的环－磷酸鸟苷酸（ｘＧＭＰ）,则导致     

止血带休克时主动脉舒缩功能与一氧化氮合酶活性的关系

目的：为探讨止血带休克发生过程中血管舒缩功能的改变及意义,以及与血管一氧化氮（ＮＯ）产生的关系。方法：采用Ｒｏｓｅｎｔｈａｌ方法复制大鼠止血带休克（ＴｏＳ）模型,分别测定对照组和ＴｏＳ组大鼠血浆中,主动脉孵育液中亚硝酸盐（ＮＯ－２）含量及主动脉组织中ｃＧＭＰ含量,一氧化氮合酶（ＮＯＳ）活性,同时观察了主动脉血管环舒缩功能的改变。结果：ＴｏＳ大鼠离体主动脉环对去甲肾上腺素的反应性降低;其血浆和主动脉孵育液中ＮＯ－２明显增加;主动脉ｃＧＭＰ含量增多;主动脉血管总ＮＯＳ活性加强,其中主要是诱导型ＮＯＳ（ｉＮＯＳ）活性增加。结论：ＴｏＳ大鼠主动脉ＮＯＳ活性加强,产生ＮＯ增多,造成血管低反应性。     

EDRF对PE引起的大鼠主动脉缩血管效应的作用

本文研究ＥＤＲＦ（ｅｎｄｏｔｈｅｌｉｕｍ－ｄｅｒｉｖｅｄｒｅｌａｘｉｎｇｆａｃｔｏｒ,ＥＤＲＦ）对ＰＥ（ｐｈｅｎｙｌｅｐｈｒｉｎｅ）引起的大鼠主动脉收缩反应的影响。内皮完整和去内皮的大鼠主动脉环悬挂于器官浴槽中,测定血管的张力和收缩速度的变化。所有的实验在消炎痛（ｉｎｄｏｍｅｔｈａｃｉｎ,１０μｍｏｌ／Ｌ）存在下进行。用美兰（ｍｅｔｈｙｌｅｎｅｂｌｕｅ,ＭＢ,１０μｍｏｌ／Ｌ）或左旋硝基精氨酸（ＮＧ－ｎｉｔｒｏ－Ｌ－ａｒｇｉｎｉｎｅ,Ｌ－ＮＮＡ,３０μｍｏｌ／Ｌ）处理内皮完整的大鼠主动脉环,ＰＥ的剂量－收缩张力曲线明显左移,ＥＣ３０值均降低５倍,最大反应比率分别为１．６±０．４和１．６±０．５。在去内皮的大鼠主动脉环中,经ＭＢ和Ｌ－ＮＮＡ处理后,仍可见ＥＣ３０下降３倍,最大反应比率均为１．０±０．２。后者可能与血管平滑肌产生少量ＥＤＲＦ有关。我们的结果提示ＰＥ对血管的收缩反应也受血管内皮和平滑肌产生的ＥＤＲＦ的调控     

缺氧复氧对家兔胸主动脉环张力的影响及其机制

生物测定法观察家兔胸主动脉环经缺氧－复氧后血管张力的变化及这种变化与内皮的关系,并初步探讨了缺氧复氧对血管张力影响的机制。结果表明急剧缺氧可使苯肾上腺素（ＰＥ）预收缩的主动脉环出现短暂的收缩,随即自发舒张,复氧后立即舒张,随后持续收缩;去除内皮或经一氧化氮（ｎｉｔｒｉｃｏｘｉｄｅ,ＮＯ）合成酶抑制剂Ｎ－硝基－精氨酸－甲基酯（Ｌ－ＮＡＭＥ）或鸟苷酸环化酶抑制剂美蓝（ＭＢ）孵育后的血管环,缺氧性收缩反应消除或明显抑制,复氧性舒张也受到明显抑制,而复氧性收缩显著增强;加入ＮＯ合成底物Ｌ－精氨酸（Ｌ－Ａｒｇ）孵育后,有内皮血管环缺氧复氧性张力变化与对照组相比无明显变化。表明缺氧性血管收缩是内皮依赖性的,与ＮＯ释放的迅即减少有关;复氧早期引起的舒张是由于内皮释放ＮＯ引起的,而随后的收缩可能因复氧后大量氧自由基灭活ＮＯ所致。     

硝基左旋精氨酸对睡眠抑制作用的机制研究

本文观察了硝基左旋精氨酸（Ｌ－ＮＮＡ,５０ｍｇ／ｋｇ,ｉｐ）和Ｌ－精氨酸（Ｌ－ａｒｇ,１１０ｍｇ／ｋｇ,ｉｐ）对慢性植入电极的大鼠睡眠－觉醒周期的影响及中缝核５－羟色胺（５－ＨＴ）神经元免疫阳性反应的变化。结果表明：Ｌ－ＮＮＡ显著抑制慢波睡眠和快眼动睡眠,使平均动脉压（ＭＡＰ）升高。Ｌ－ａｒｇ则使ＭＡＰ显著降低,对睡眠无明显影响。预先给予Ｌ－ａｒｇ可逆转Ｌ－ＮＮＡ的效应。腹腔给予Ｌ－ＮＮＡ后２ｈ,     

缺氧兔心肌血流量的变化及一氧化氮和腺苷的调节作用

观察了急性缺氧和慢性间断性缺氧兔心肌血流量、心肌组织中腺苷和ｃＧＭＰ含量的变化及Ｎ￣ω－ＮＯ３－Ｌ－精氨酸（Ｌ－ＮＡ）阻断一氧化氮（ＮＯ）生成后的影响。结果表明,急性缺氧兔心肌血流量增加,心肌组织中腺苷和ｃＧＭＰ含量增高;静脉输入Ｌ－ＮＡ后,心肌血流量减少,同时心肌组织中ｃＧＭＰ含量降低,腺苷含量进一步增高。慢性缺氧免心肌血流量无明显变化,红细胞压积（Ｈｃｔ）增高;抑制ＮＯ合成后,右室心肌血流量减少,左室心肌血流量无明显变化。说明ＮＯ和腺苷均参与急性缺氧时冠状血管扩张机制;ＮＯ参与慢性缺氧兔心肌血管基础张力调节。     

Interleukin-1beta causes different levels of nitric oxide-mediated depression of contractility in different positions of rat thoracic aorta.

Interleukin-1beta (IL-1beta) can be synthesized by macrophages, endothelial cells and vascular smooth muscle cells when stimulated by bacterial lipopolysaccharide (endotoxin) during septic shock. The IL-1beta levels in the blood vessel wall are also elevated in atherosclerosis. IL-1beta can cause induction of inducible nitric oxide synthase (iNOS) expression in vascular smooth muscle cells and produce vasorelaxation, hypotension and ultimately tissue damage. We studied the depressions of vascular smooth muscle contractions at 3 hours after exposure to IL-1beta in different positions of rat thoracic aorta. The data show that the aortic rings from the cranial end of rat thoracic aorta had little response to IL-1beta (0.5 and 1.0 ng/ml) while those from the caudal end of thoracic aorta had larger depressant response. S-methylisothiourea sulfate (SMT), an iNOS inhibitor, completely blocked the depression of contraction caused by IL-1beta in intact aortic rings. If the endothelium was removed from the aortic rings before exposure to IL-1beta, all rings from different parts of the thoracic aorta showed an equal amount of vasodepression. Thus, the difference in the depressant response of IL-1beta in different portions of thoracic aorta is endothelium-dependent and involves induction of NOS.     

Reversible changes in stress fiber expression and cell shape in regenerating rat and rabbit aortic endothelium

The influence of intimal de-endothelialization on stress fiber expression in regenerating rat and rabbit aortic endothelium was studied using immunofluorescence microscopy. Rat thoracic and abdominal aortae were balloon de-endothelialized, and endothelial cell shape and stress fiber expression was studied in both uninjured and de-endothelialized animals. In control animals, the majority of thoracic endothelial cells did not contain stress fibers while the majority of abdominal endothelial cells did. One week after injury, all the endothelial cells distal to the regenerating edge contained very prominent stress fibers. In areas directly adjacent to the still de-endothelialized surface, the endothelial cells had an intense, diffuse cytoplasmic staining without stress fibers. Regenerating endothelium also had a substantially higher length-to-width ratio, but smaller cell areas. Six weeks after injury, the endothelium had completely regenerated, and stress fibers were lost from the majority of the thoracic endothelial cells. Changes in abdominal aorta stress fiber expression were not as marked. In the rabbit, all the control thoracic endothelial cells had stress fibers; however, cells at the leading edge of a narrow region of de-endothelialization had few stress fibers. The results suggest that stress fibers do not play a primary role in cellular migration in situ. The transient increase in stress fiber expression in the rat may result from a temporary demand for greater adhesive capabilities until the subendothelial extracellular matrix is remodeled.     

Vasodilatory action mechanisms of apigenin isolated from Apium graveolens in rat thoracic aorta.

The effect of apigenin, isolated from Apium graveolens, on the contraction of rat thoracic aorta was studied. Apigenin inhibited the contraction of aortic rings caused by cumulative concentrations of calcium (0.03-3 mM) in high potassium (60 mM) medium, with an IC50 of about 48 microM. After pretreatment it also inhibited norepinephrine (NE, 3 microM)-induced phasic and tonic contraction in a concentration (35-140 microM)-dependent manner with an IC50 of 63 microM. At the plateau of NE-induced tonic contraction, addition of apigenin caused relaxation. This relaxing effect of apigenin was not antagonized by indomethacin (20 microM) or methylene blue (50 microM), and still existed in endothelial denuded rat aorta or in the presence of nifedipine (2-100 microM). Neither cAMP nor cGMP levels were changed by apigenin. Both the formation of inositol monophosphate caused by NE and the phasic contraction induced by caffeine in the Ca(2+)-free solution were unaffected by apigenin. 45Ca2+ influx caused by either NE or K+ was inhibited by apigenin concentration-dependently. It is concluded that apigenin relaxes rat thoracic aorta mainly by suppressing the Ca2+ influx through both voltage- and receptor-operated calcium channels.     

Involvement of Ad4BP/SF-1, DAX-1, and COUP-TFII transcription factor on steroid production and luteinization in ovarian theca cells

The link between chronic alcohol consumption and cardiovascular injury including hypertension is well known. However, molecular mediators implicated with alcohol-induced elevation in blood pressure (BP) remain elusive. The aim of this study was to investigate the relationship of chronic ethanol-induced endothelial injury and elevation in BP with angiotensin II levels in rats. Male Fisher rats were divided into two groups of seven animals each and treated as follows: (1) Control (5% sucrose, orally) daily for 12 weeks and (2) ethanol (4 g kg⁻¹, orally) daily for 12 weeks. The BP (systolic, diastolic, and mean) was recorded every week. The animals were anesthetized with pentobarbital after 12 weeks; blood and thoracic aorta were isolated and analyzed for aortic reactivity response, angiotensin II levels, and oxidative endothelial injury. The results show that the systolic, diastolic, and mean BP were significantly elevated 12 weeks after ethanol ingestion. The increased BP was related to elevated angiotensin II levels in the plasma and aorta of alcohol treated group compared to control. The aortic NADPH oxidase activity, ratio of oxidized to reduced glutathione (GSSG/GSH) and lipid peroxidation significantly increased, whereas nitric oxide (NO), endothelial NO synthase (eNOS), and vascular endothelial growth factor (VEGF) protein expressions were depressed in alcohol group compared to control. The phenylephrine-mediated vasoconstriction response was not altered, while acetylcholine-mediated vasorelaxation response was depressed in the aorta of ethanol treated rats compared to control. It is concluded that chronic ethanol ingestion induces hypertension which is correlated with elevated tissue angiotensin II levels, activation of NADPH oxidase activity causing endothelial injury, depletion of endothelial NO generating system, and impaired vascular relaxation in rats.     

Vibrio vulnificus hemolysin dilates rat thoracic aorta by activating guanylate cyclase

Hemolysin produced by Vibrio vulniflcus caused hypotension and tachycardia in rats and dilated rat thoracic aorta. Hemolysin-induced vasodilatation of the aorta was not affected by Nω-nitro-L-arginine methyl ester and aminoguanidine, NO synthase inhibitors, whereas the vasodilatation was inhibited by LY 83,583, a guanylate cyclase inhibitor. Hemolysin elevated cGMP levels, and the elevation was abolished by LY 83,583. These results suggest that V. vulnificus hemolysin activates guanylate cyclase independently of NO synthase, and the subsequent increase in cGMP levels results in vasodilatation.     

Hydroxyl radicals mediate injury to endothelium-dependent relaxation in diabetic rat

The purpose of this study was to determine the radical species which mediates the toxic effects of exogenous oxygenderived free radicals on endothelial function of chronic diabetic rat aorta. Endothelium-dependent relaxation to acetylcholine was impaired in diabetic vessels. Exposure to the exogenous free radical generating system of xanthine plus xanthine oxidase selectively impaired endothelium-dependent relaxation to acetylcholine in control and diabetic aorta with relaxations essentially abolished in diabetic aorta. The loss of relaxation to acetylcholine in diabetic aorta was prevented or attenuated by pretreatment with catalase, dimethylthiourea or desferrioxamine, but not by mannitol or superoxide dismutase. These results suggest that hydroxyl radicals play an important role in the endothelial injury produced by oxygen-derived free radicals in chronic diabetic rat aorta. Furthermore, the site of the injury is likely due to intracellular generation of hydroxyl radicals.     

Erythropoietin attenuates the sequels of ischaemic spinal cord injury with enhanced recruitment of CD34+ cells in mice

Erythropoietin has been shown to promote tissue regeneration after ischaemic injury in various organs. Here, we investigated whether Erythropoietin could ameliorate ischaemic spinal cord injury in the mouse and sought an underlying mechanism. Spinal cord ischaemia was developed by cross-clamping the descending thoracic aorta for 7 or 9 min. in mice. Erythropoietin (5000 IU/kg) or saline was administrated 30 min. before aortic cross-clamping. Neurological function was assessed using the paralysis score for 7 days after the operation. Spinal cords were histologically evaluated 2 and 7 days after the operation. Immunohistochemistry was used to detect CD34(+) cells and the expression of brain-derived neurotrophic factor and vascular endothelial growth factor. Each mouse exhibited either mildly impaired function or complete paralysis at day 2. Erythropoietin-treated mice with complete paralysis demonstrated significant improvement of neurological function between day 2 and 7, compared to saline-treated mice with complete paralysis. Motor neurons in erythropoietin-treated mice were more preserved at day 7 than those in saline-treated mice with complete paralysis. CD34(+) cells in the lumbar spinal cord of erythropoietin-treated mice were more abundant at day 2 than those of saline-treated mice. Brain-derived neurotrophic factor and vascular endothelial growth factor were markedly expressed in lumbar spinal cords in erythropoietin-treated mice at day 7. Erythropoietin demonstrated neuroprotective effects in the ischaemic spinal cord, improving neurological function and attenuating motor neuron loss. These effects may have been mediated by recruited CD34(+) cells, and enhanced expression of brain-derived neurotrophic factor and vascular endothelial growth factor.     

Pharmacological evaluation of GS-389, a novel tetrahydroisoquinoline analog related to higenamine, on vascular smooth muscle.

The effects of GS-389, a novel tetrahydroisoquinoline analog, on isolated rat and mouse thoracic aorta rings, were investigated. Both GS-389 and papaverine induced endothelium-independent, concentration-dependent relaxations of the rat and mouse aortae precontracted with phenylephrine (PE). The GS-389-induced inhibition of the contractile response to PE was noncompetitive. The initial phasic contraction to PE elicited in Ca(2+)-free media was also attenuated by pretreatment with GS-389, indicating that GS-389 may interfere with the release of intracellular Ca2+ and/or the effects of intracellular Ca2+ release. GS-389 potentiated the vasodilatory effects of isoproterenol and sodium nitroprusside in rat and mouse aortae. GS-389 significantly increased cGMP levels in the rat aorta and inhibited cGMP phosphodiesterase from the rabbit brain. Methylene blue, but not propranolol, inhibited the vasodilatory effect of GS-389. These results suggest that the vasorelaxant effect of GS-389 may be due, at least in part, to inhibition of cGMP metabolism.     

Effect of NO donors on protein phosphorylation in intact vascular and nonvascular smooth muscles

It is generally well accepted that nitrovasodilator-induced relaxation of vascular smooth muscle involves elevation of cGMP and activation of a specific cGMP-dependent protein kinase [protein kinase G (PKG)]. However, the protein targets of PKG and the underlying mechanisms by which this kinase leads to a relaxant response have not been elucidated. Several types of smooth muscle, including rat myometrium and vas deferens, are not relaxed by sodium nitroprusside, even at concentrations that produce marked elevation of cGMP and activation of PKG. The main objective of our studies was to compare PKG-mediated protein phosphorylation in intact rat aorta, rat myometrium, and rat vas deferens using two-dimensional gel electrophoresis. In intact rat aorta, seven PKG substrates were detected during relaxation of the tissue. None of the PKG substrates identified in the rat aorta appeared to be phosphorylated in the myometrium or vas deferens after administration of various cGMP-elevating agents. Thus the failure of the rat myometrium and rat vas deferens to relax in the face of cGMP elevation and PKG activation may be due to a lack of PKG substrate phosphorylation.