Peptide 204-212 of lipocortin 5 inhibits the generation of a prostacyclin-like factor from rat aorta preparations in vitro.

The release of an endogenous prostacyclin-like factor (PLF) from rat thoracic aorta rings was evaluated through inhibition of platelet ADP-induced aggregation and assessed with a micro-method using 96-multiwell plates. Aggregation was assessed in an ELISA reader by measuring changes of optical density at 620 nm in each well. The generation of endogenous PLF by aortic rings was time-dependent and was inhibited by indomethacin (3 microM). ADP-induced aggregation was inhibited by iloprost in a dose-dependent manner. Incubation of rat aorta rings with peptide 204-212 of human lipocortin 5 (1-100 micrograms/ml) resulted in a dose-dependent inhibition of PLF release with a maximal inhibition of 90-95%. The effect of peptide 204-212 was reversible. A control peptide (amino-acids 104-112 of lipocortin 5) was without any significant effect. Peptide 204-212 (100 micrograms/ml) did not modify PLF release from rat aorta preparations challenged with arachidonic acid (10(-6)-10(-4) M).     

Effects of a newly synthesized leukotriene antagonist, NZ-107, on immediate-type hypersensitivity reaction in rats and guinea-pigs.

The effects of 4-bromo-5-(3-ethoxy-4-methoxybenzylamino)-3(2H)-pyridazinone (NZ-107) on immediate type hypersensitivity reactions in rats and guinea-pigs were studied. 1. When NZ-107, at a dose of 50 mg/kg (i.p.) or 100 mg/kg (orally), was administered to rats, 48-h homologous passive cutaneous anaphylaxis (PCA) reaction and histamine-, leukotriene C4 (LTC4)- and leukotriene D4 (LTD4)-induced skin reactions were suppressed by the agent. 2. NZ-107 (10(-6) g/ml) inhibited both LTC4- and LTD4-induced contractions of isolated rat stomach smooth muscle. 3. NZ-107 inhibited antigen-induced histamine release from rat peritoneal mast cells by 26% at a concentration of 10(-4) g/ml. 4. NZ-107, at doses of 25 and 50 mg/kg (orally), significantly inhibited guinea-pig 3-h heterologous PCA reaction. 5. NZ-107 inhibited antigen-induced histamine release from guinea-pig lung tissue by 17% and 48% at concentrations of 5 x 10(-5) and 10(-4) g/ml, respectively. 6. NZ-107, at doses of 25 and 50 mg/kg (i.p.), inhibited antigen-induced bronchoconstriction and eosinophil accumulation in the bronchoalveolar lavage fluid (BALF) of guinea-pigs. These results suggest that NZ-107 has anti-allergic action including inhibition of eosinophil accumulation in an antigen-challenged airway lesion in rats and guinea-pigs. The anti-allergic action of this agent is thought to be due to its action as a histamine and LT antagonist and its consequent inhibition of antigen-induced histamine release.     

EDRF-release and Ca+(+)-channel blockade by magnolol, an antiplatelet agent isolated from Chinese herb Magnolia officinalis, in rat thoracic aorta

Magnolol is an antiplatelet agent isolated from Chinese herb Magnolia officinalis. It inhibited norepinephrine (NE, 3 microM)-induced phasic and tonic contractions in rat thoracic aorta. At the plateau of the NE-induced tonic contraction, addition of magnolol caused two phases (fast and slow) of relaxation. These two relaxations were concentration-dependent (10-100 micrograms/ml), and were not inhibited by indomethacin (20 microM). The fast relaxation was completely antagonized by hemoglobin (10 microM) and methylene blue (50 microM), and disappeared in de-endothelialized aorta while the slow relaxation was not affected by the above treatments. Magnolol also inhibited high potassium (60 mM)-induced, calcium-dependent (0.03 to 3 mM) contraction of rat aorta in a concentration-dependent manner. 45Ca(+)+ influx induced by high potassium or NE was markedly inhibited by magnolol. Cyclic GMP, but not PGI2, was increased by magnolol in intact, but not in de-endothelialized aorta. It is concluded that magnolol relaxed vascular smooth muscle by releasing endothelium-derived relaxing factor (EDRF) and by inhibiting calcium influx through voltage-gated calcium channels.     

Effects of veratrine and paeoniflorin on isolated mouse vas deferens

In this study, we attempted to identify the interactions and mechanisms between veratrine and paeoniflorin on isolated mouse vas deferens. Paeoniflorin had no effect on isolated mouse vas deferens. Veratrine (1 x 10(-5) approximately 1 x 10(-3) g/ml) could directly induce contraction of isolated rat and mouse vas deferens. The concentration induced by veratrine (1 x 10(-5) g/ml) was completely inhibited by Ca2+-free solution and verapamil (1 x 10(-5) M), in both the epididymal and the prostatic portions of isolated mouse vas deferens. Naloxone (1 x 10(-5) M) did not alter the contraction induced by veratrine (1 x 10(-5) g/ml) in either the epididymal or the prostatic portions of isolated mouse vas deferens. Paeoniflorin (4.8 x 10(-5) g/ml) inhibited the contraction induced by veratrine (1 x 10(-5) g/ml) in both the epididymal and the prostatic portions of isolated mouse vas deferens. Paeoniflorin (4.8 x 10(-5) g/ml) potentiated norepinephrine (1 x 10(-5) M)-induced phasic contraction in the epididymal portion, but decreased contractions in the prostatic portion. Paeoniflorin (4.8 x 10(-5) g/ml) increased KCI (56 mM)-induced phasic contraction in the epididymal portion, but decreased the tonic contraction in either the epididymal or the prostatic portion. Veratrine (1 x 10(-5) g/ml)-induced contractions could be decreased by pretreatment with ryanodine (1 x 10(-5) M) in both the epididymal and the prostatic portions. Pretreatment with the combination of paeoniflorin (4.8 x 10(-5) g/ml) and ryanodine (1 x 10(-5) M) did not potentiate the inhibition of paeoniflorin in the veratrine-induced contraction in both the epididymal and the prostatic portions of isolated mouse vas deferens.     

Neutrophil-derived relaxing factor relaxes vascular smooth muscle through a cGMP-mediated mechanism

Neutrophils harvested from the peritoneal cavities of rats have been shown to release a factor that relaxes precontracted aorta and has a pharmacologic profile similar to that previously reported for endothelium-derived relaxing factor (EDRF). The present study was designed to determine if this neutrophil-derived relaxing factor (NDRF) relaxes rat aortic smooth muscle by affecting the intracellular cGMP levels. Aortic sheets (endothelium removed) were incubated in organ chambers in a physiological salt solution containing phenylephrine (1 x 10(-7) M) and superoxide dismutase (10 or 100 U/ml). Basal cGMP levels (10-15 pmoles/g tissue) were not affected by the incubation reagents. Neutrophils (3 x 10(6) to 1 x 10(8) cells/10 ml) increased cGMP, but not cAMP, levels in a cell number-dependent manner. Peak induction occurred at 5 min of incubation. Methylene blue (1 x 10(-5) M) inhibited and zaprinast (1 x 10(-5) M) potentiated the neutrophil-induced increases in cGMP. The data thus support the hypothesis that neutrophil-induced vascular smooth muscle relaxation is mediated through a factor, NDRF, which increases intracellular cGMP levels.     

Effects of a thromboxane synthetase inhibitor and a thromboxane antagonist on release and activity of thromboxane A2 and prostacyclin in vitro

The TxA2 synthetase inhibitor, dazoxiben, and the TxA2 antagonist, +/- SQ 29,548, were examined for effects on release and vasoactivity of TxA2 and prostacyclin. Isolated perfused guinea pig lungs were used as the enzyme source from which TxA2 and prostacyclin were released in response to injections of arachidonic acid or bradykinin. Both dazoxiben and +/- SQ 29, 548 inhibited contraction of the superfused rat aorta and bovine coronary artery after arachidonic acid injection through the lung. +/- SQ 29,548 abolished contractions of the rat aorta, but significant aorta contracting activity persisted during dazoxiben treatment. Dazoxiben significantly inhibited arachidonate-induced release of TxA2 (immunoreactive TxB2) into the superfusate, but TxA2 release was significantly potentiated by +/- SQ 29,548. Thus, in the presence of enhanced TxA2 concentrations, +/- SQ 29,548 effectively antagonized the vasospastic effect of TxA2. Dazoxiben diverted a significantly greater amount of arachidonic acid into prostacyclin synthesis (immunoreactive 6-keto-PGF1 alpha), changing original coronary vasoconstriction into relaxation. +/- SQ 29,548 did not significantly modify lung prostacyclin synthesis. Moreover, with +/- SQ 29,548, the absence of TxA2-mediated coronary contraction unmasked active relaxation of the superfused bovine coronary artery, coincident with thromboxane and prostacyclin release. Dazoxiben consistently inhibited TxA2 synthesis and enhanced prostacyclin synthesis. +/- SQ 29,548 augmented TxB2 release in response to arachidonate, but not bradykinin, and did not significantly alter 6-keto-PGF1 alpha release in response to either arachidonate or bradykinin. In terms of vasoactivity measured in vitro, +/- SQ 29,548 and dazoxiben produced similar anti-vasospastic effects, although this was accomplished by completely different mechanisms.     

Enhancement of anaphylactic mediator release from guinea-pig perfused lungs by fatty acid hydroperoxides.

Fragments of chopped lung from indomethacin treated guinea-pigs had an anti-aggregating effect when added to human platelet rich plasma (PRP), probably due to the production of prostacyclin (PGI2) since the effect was inhibited by 15-hydroperoxy arachidonic acid (15-HPAA, 10 micrograms ml(-1)). Both 15-HPAA (1-20 micrograms ml(-1) min (-1)) and 13-hydroperoxy linoleic acid (13-HPLA, 20 micrograms ml(-1) min(-1)) caused a marked enhancement of the anaphylactic release of histamine, slow-reacting substance of anaphylaxis (SRS-A) and rabbit aorta contracting substance (RCS) from guinea-pig isolated perfused lungs. This enhancement was not reversed by the concomitant infusion of either PGI2 (5 micrograms ml(-1) min (-1)) or 6-oxo-prostaglandin F1alpha (6-oxo-PGF1alpha, 5 micrograms ml(-1) min(-1)). Anaphylactic release of histamine and SRS-A from guinea-pig perfused lungs was not inhibited by PGI2 (10 ng - 10 microgram ml(-1) min(-1)) but was inhibited by PGE2 (5 and 10 micrograms ml(-1) min (-1)). Antiserum raised to 5,6-dihydro prostacyclin (PGI1) in rabbits, which also binds PGI2, had no effect on the release of anaphylactic mediators. The fatty acid hydroperoxides may enhance mediator release either indirectly by augmenting thromboxane production or by a direct effect on sensitized cells. Further experiments to distinguish between these alternatives are described in the accompanying paper (27).     

Calcium mobilization as the endothelium-independent mechanism of action involved in the vasorelaxant response induced by the aqueous fraction of the ethanol extract of Albizia inopinata G. P. Lewis (AFL) in the rat aorta.

In a previous work, we demonstrated that, in normotensive rats, AFL induced a marked hypotension due to a decrease in total peripheral resistances (TPR), partially secondary to the release of NO by the endothelium. NO did not, however, account for the total vasodilation produced by AFL in these rats. The aim of this study was to determine the involvement of the intracellular calcium mobilization in the vasorelaxant action induced by AFL in the rat aorta. In aorta of normotensive rats AFL (10, 20, 40 and 80 microg/ml) inhibited the sustained contractions induced by KCl (80 and 30 mM) and phenylephrine (Phe, 1 microM) with similar IC50 values (54 +/- 6, 52 +/- 4 and 65 +/- 4 microg/ml, respectively). The relaxing response induced by AFL against Phe-induced contractions was modified significantly by the endothelium removal (IC50 = 132 +/- 23 and 65 +/- 4 microg/ml, endothelium removed and intact endothelium aortic rings, respectively). Nevertheless, removal of the endothelium did not significantly change IC50 values when KCl (30 and 80 mM) was used as the contractile agent. The inhibitory effect induced by AFL on high (64.5 mM) K+-induced contraction was potentiated slightly (p < 0.05) by the decrease (from 2.5 to 0.3 mM, Ca2+) and attenuated by the increase (from 2.5 to 7.5 mM Ca2+) in the external [Ca2+]. In addition, in aortas from normotensive rats, AFL antagonized transient contractions induced in Ca2+-free media induced by 1 microM noradrenaline in a concentration-dependent manner, but not those induced by 20 mM caffeine. It is suggested that the remaining vasodilator effect of AFL in normotensive rats is probably due to an inhibition of Ca2+ influx and/or inhibition of intracellular Ca2+ mobilization from the noradrenaline-sensitive stores.     

Mechanism of vasorelaxant activity of a fraction of root extract of Sesamum indicum Linn

The petroleum ether soluble fraction (SIPE) of the root extract of S. indicum was evaluated for the vasorelaxant activity using isolated rat aorta. SIPE up to 180 microg/ml concentration significantly inhibited phenylephrine- and KCl-induced contraction to the extent of 98.13 +/- 6.37 and 70.19 +/- 3.43% respectively in isolated rat aorta in a concentration dependent manner. The vasorelaxant activity was not blocked by propranolol (10 microM), atropine (1 microM) indomethacin (10 microM) and glibenclamide (10 microM). Influence of SIPE on phenylephrine-induced contractions in aortic preparations in absence of functional endothelium and on pre-incubating the tissue with L-NAME (300 microM) or methylene blue (10 microM) was also studied. SIPE at 180 microg/ml concentration could elicit partial relaxation in presence of L-NAME or methylene blue to the extent of 34.26 +/- 6.13 and 25.66 +/- 10.95% respectively. However, in absence of functional endothelium, SIPE exhibited little relaxation to the extent of 6.70 +/- 4.87%. These studies revealed that the vasorelaxant activity of SIPE was chiefly mediated through endothelium-dependent pathway.     

Effect of ethmozine on action potentials and myocardial contraction in guinea pigs

Ethmozine decreased the maximum rate of action potential rise (Vmax) in a dose-dependent manner. Using the Scatchard plot the apparent dissociation constant was calculated to be 1.52 X 10(-5) g/ml. Ethmozine also decreased the force of contraction in the concentration range between 1 X 10(-6) and 1 X 10(-4) g/ml with the apparent dissociation constant obtained from the Scatchard plot being equal to 1.48 X 10(-5) g/ml. The linear correlation coefficient between the decrease in Vmax and the decrease in the force of contraction was found to be equal to 0.998. Negative inotropic action of ethmozine was less pronounced when the stimulation frequency had been switched from 0.8 to 0.1 Hz. The decrease in Vmax under the action of ethmozine (3 X 10(-5) g/ml) was diminished from 56 +/- 7% (0.8 Hz) to only 3 +/- 8% (0.1 Hz). This was accompanied by the decrease in the negative inotropic effect: from 58 +/- 9% (0.8 Hz) to 16 +/- 15% (0.1 Hz). It was assumed that the negative inotropic action of ethmozine was mediated by the Na--Ca exchange, which was inhibited by the decrease of the intracellular Na+ concentration due to the blockade of sodium channels by ethmozine.     

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。     

Proinflammatory cytokines alter/reduce esophageal circular muscle contraction in experimental cat esophagitis

Cholinergic mechanisms are largely responsible for esophageal contraction in response to swallowing or to in vitro electrical field stimulation (EFS). After induction of experimental esophagitis by repeated acid perfusion, the responses to swallowing and to EFS were significantly reduced but contraction in response to ACh was not affected, suggesting that cholinergic mechanisms are damaged by acid perfusion but that myogenic mechanisms are not. Measurements of ACh release in response to EFS confirmed that release of ACh was reduced in esophagitis compared with normal controls. To examine factors contributing to this neuropathy, normal esophageal strips were incubated for 1-2 h with the proinflammatory cytokines IL-1beta (100 U/ml), IL-6 (1 ng/ml), or TNF-alpha (1 ng/ml). IL-1beta and IL-6 levels, measured by Western blot analysis, increased in esophagitis compared with normal circular muscle. IL-1beta and IL-6 reduced contraction in response to EFS (2-10 Hz, 0.2 ms) but did not affect ACh-induced contraction, suggesting that these cytokines inhibit ACh release without affecting myogenic contractile mechanisms. EFS-induced ACh release was significantly reduced in normal esophageal strips by incubation in IL-1beta or IL-6, suggesting that they may contribute to the contractility changes. TNF-alpha at 1 ng/ml, however, did not affect the response to ACh or to electrical stimulation but inhibited both at higher concentrations. TNF-alpha levels were low in normal muscle and did not increase with esophagitis. The data suggest that the proinflammatory cytokines IL-1beta and IL-6 contribute to reduced esophageal contraction by inhibiting release of ACh from myenteric neurons.     

Vascular smooth muscle relaxation by a lectin from Pisum arvense: evidences of endothelial NOS pathway

The vasorelaxant effect of the lectin of Pisum arvense (PAL) seeds was investigated in rat aorta. PAL (10-100 μg/ml) was applied on aorta rings, with or without endothelium, pre-contracted with phenylephrine (Phe; 0.1 μM). Participation of endothelium derived relaxant factors was evaluated incubating the tissue with indomethacin (10 μM), L-nitro arginine methyl ester (L-NAME, 100 μM) and tetraethylammonium (TEA, 5 mM) before addition of PAL. The role of the lectin domain was investigated by addition of PAL into tissue in presence of glucose (3x 10?? M), or N-acetyl Dglucosamine (GlcNAc; 3 x 10?? M). The importance of extracellular calcium (Ca2?e) or interaction with muscarinic receptors in the relaxant effect was evaluated by addition of PAL into aorta rings containing calcium free solution (OCa) and atropine (1 μ M), respectively. PAL induced concentration-dependent relaxation in endothelized aorta (IC50 =58.38 ± 1.87 μg/ml), which was reversed by L-NAME and glucose. The lectin effect was totally inhibited when the preparation was inserted in OCa, but not in presence of atropine. Summarizing, our data showed a relaxant effect of PAL in isolated rat aorta rings in presence of endothelium, suggestive of interaction between the lectin carbohydrate binding sites with specific receptors located in vascular endothelial cells leading to nitric oxide synthase activation. This effect seems to require Ca2?e but is independent on muscarinic receptors interaction.     

Differential contractile actions of reactive oxygen species on rat aorta: selective activation of ATP receptor by H2O2

This study aims to examine the effects of different reactive oxygen species (ROS) on the resting tension of endothelium-denuded rat aortic rings. In these preparations, H2O2 (30 microM) induced a fast and transient contraction, which could be abolished by pretreatment of catalase (800 U/ml), but not affected by superoxide anion scavenger, superoxide dismutase (SOD; 150 U/ml) or the hydroxyl free radical scavenger, DMSO/mannitol (each 3 mM). In contrast, pyrogallol, a putative superoxide anion donor, induced a biphasic contraction, which could be abolished by SOD, but not by catalase or DMSO/mannitol. Unlike H2O2 and pyrogallol, Vitamin C(VitC)/Fe2+ (each 100 microM), a commonly used hydroxyl radical-generating system, triggered a tonic contraction which could be prevented by DMSO/mannitol, but not by SOD or catalase. Interestingly, H2O2-induced contraction could be concentration-dependently (10-100 microM) inhibited by suramin and reactive blue-2 (RB-2), two widely used ATP receptor antagonists. On the other hand, suramin or RB-2, at concentration up to 100 microM, affected neither pyrogallol nor VitC/Fe2+-induced contraction. In conclusion, we showed for the first time that different ROS could contract rat aorta with different mechanisms of action, and H2O2 elicits a transient contraction probably as a result of the ATP receptor activation.     

Xanthorrhizol induces endothelium-independent relaxation of rat thoracic aorta

Xanthorrhizol, a bisabolene isolated from the medicinal plant Iostephane heterophylla, was assayed on rat thoracic aorta rings to elucidate its effect and likely mechanism of action, by measuring changes of isometric tension. Xanthorrhizol (1, 3, 10, 30 and 100 microg/mL) significantly inhibited precontractions induced by KCI-; (60mM), noradrenaline (10(-6) M) or CaCl2 (1.0 mM). Increasing concentrations of external calcium antagonized the inhibitory effect on KCl-induced contractions. The vasorelaxing effect of xanthorrhizol was not affected by indomethacin (10 microM) or L-NAME (100 microM) in intact rat thoracic aorta rings precontracted by noradrenaline, which suggested that the effect was not mediated through either endothelium-derived prostacyclin (PGI2) or nitric oxide release from endothelial cells. Endothelium removal did not affect the relaxation induced by xanthorrhizol on rat thoracic aorta rings, discarding the participation of any substance released by the endothelium. Xanthorrhizol inhibitory effect was greater on KCI- and CaCl2-induced contractions than on those induced by noradrenaline. Xanthorrhizol inhibitory effect in rat thoracic aorta is likely explained for interference with calcium availability by inhibiting calcium influx through both voltage- and receptor-operated channels.     

Mechanisms of the contractile effect of the hydroalcoholic extract of Cissampelos sympodialis Eichl. in the rat aorta.

In the present work the effect of the aqueous fraction of the ethanolic extract of the leaves (AFL) of Cissampelos sympodialis Eichl. was investigated in the rat aorta. In the presence of functional endothelium, AFL produced concentration-dependent contractions (EC50 value of 76.6 +/- 17.8 micrograms/ml). In the absence of functional endothelium, the concentration-response curves to AFL were significantly shifted to the left (EC50 values of 1.3 +/- 0.9 micrograms/ml) without modification of its maximal contractile effect. In the presence of L-NAME (300 microM) and of indomethacin (10 mM), the concentration-response curves produced by AFL were also shifted to the left (EC50 values of 21.8 +/- 6.2 and 24.3 +/- 13.2 micrograms/ml, respectively). The treatment of the aortas with L-NAME (300 microM) plus indomethacin (10 microM) produced a significant shift to the left of the concentration-dependent curves of AFL (EC50 value of 4.9 +/- 2.2 micrograms/ml), similar to that observed in the absence of the vascular endothelium. In addition, AFL-induced contraction was abolished in the presence of prazosin (1 microM), and significantly shifted to the right in the presence of yohimbine (EC50 value of 723.6 +/- 76.4 micrograms/ml). Thus, based on these results, it can be concluded that contractions induced by AFL in the rat aorta were due to activation of alpha-adrenoceptors. Furthermore, these results also showed that the AFL-induced contractions were modulated by the endothelium, via the release of NO and of a cyclooxygenase-derived relaxant product. Finally, it can be concluded that the contractile effects of AFL on vascular smooth muscle may play an important role in the hypertensive effects of this plant in vivo.     

Apple procyanidins induce hyperpolarization of rat aorta endothelial cells via activation of K+ channels

Apple procyanidins (AP), one of the polyphenol-rich compounds, showed an endothelial-dependent vasorelaxation in rat aorta, but the mechanisms of beneficial effects are still unclear. The present study was designed to clarify the potential role of AP in rat aorta endothelial cells (RAECs). The treatment of RAECs with AP (1-10 μg/ml) resulted in a dose-dependent hyperpolarization with a maximum effect at 10 μg/ml, and for this reason, AP (10 μg/ml) was used in all the following experiments. AP-induced hyperpolarization was significantly inhibited by pretreatment of nonspecific K(+) inhibitor, tetraethyl ammonium chloride or specific K(+) channel inhibitors, iberiotoxin, glibenclamide, 4-aminopyridine and BaCl(2), as well as by high KCl or Ca(2+)-free solution. AP-induced hyperpolarization was also proved using 64-channel multielectrode dish system that can monitor a direct and real-time change of membrane potential. Furthermore, AP treatment caused a significant increase of nitric oxide (NO) production and cyclic guanosine monophosphate levels via endothelial NO synthase messenger RNA expression. The NO production was inhibited by N(G)-monoethyl-l-arginine or Ca(2+)-free solution and was completely abolished by their combination. Also, AP inhibited endothelial proliferation, while the effect was significantly abolished by N(G)-monoethyl-l-arginine or tetraethyl ammonium chloride. These findings suggest that AP induces both hyperpolarization of RAECs via multiple activation of K(+) channels and activation of NO/cyclic guanosine monophosphate pathway via increasing NO production or is responsible for antiangiogenic effect. Diminishment of hyperpolarization as well as NO production of AP in Ca(2+)-free solution implicated that AP would play a crucial role in promoting Ca(2+) influx into endothelial cells so as to promote both actions.     

Nitric oxide dependent and independent effects of in vitro incubation or endotoxin on vascular reactivity in rat aorta.

We sought to delineate contributions of nitric oxide (NO) and other mechanisms to impairment of contraction and endothelium-dependent relaxation following prolonged in vitro incubation, endotoxin and interleukin-1 exposure in isolated rat aorta. Responses from freshly-dissected (control) rings +/-endothelium were compared with those from rings incubated in sterile, antibiotic containing medium +/- E. Coli endotoxin (LPS, 100 microg/ml) +/- interleukin-1 (IL-1, 40 ng/ml) at 37 degrees C for 20-24 h. In some experiments, medium included dexamethasone (DEX, 1 microg/ml), cycloheximide (10 microg/ml), or N(G)-nitro-L-arginine (NNLA, 10(-4)M). After incubation, medium nitrite was measured. Incubation alone, without addition of inflammatory mediators, impaired contraction in an agonist-specific manner, by both NO-dependent and NO-independent mechanisms. Either LPS or IL-1 diminished contraction further, in a similarly heterogeneous manner. For example, contractions were changed in LPS-incubated endothelium-intact rings (vs. fresh controls) by -85%, +115%, -15%, -96%, and -37% for phenylephrine (PE), serotonin, prostaglandin F2alpha, angiotensin II, and U46619, respectively. NO synthase inhibition with NNLA either following, or during LPS incubation only partially normalized subsequent PE contractions, an effect which was smaller than that of DEX. Nitrite accumulation was inversely proportional to PE response, even though NO was not the sole mediator of LPS-impaired contraction. LPS and IL-1 nearly abolished ACh-induced relaxation, which was only mildly impaired by incubation alone. We conclude that prolonged incubation impaired vasoconstriction via both NO synthase induction and NO-independent mechanisms. LPS or IL-1 incubation impaired vasoconstriction further, primarily by NO-independent mechanisms. Moreover, vasoconstrictor responses following LPS varied with the agonist's ability to modulate endothelial NO release. These results are in accord with the failure of NO synthase inhibition to fully restore systemic vascular resistance indices in experimental endotoxemia or in hyperdynamic septic patients.     

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.     

白细胞介素—10对血管一氧化氮／一氧化氮合酶系统的影响

为探讨抗炎因子－－白细胞介素－10（IL－10）对大鼠主动脉一氧化氮（NO）／一氧化氮合酶（NOS）系统的影响,应用Griess试剂、^3H－瓜氨酸生成及蛋白免疫印迹杂交等方法,测定IL－10孵育对血管NO释放、NOS活性及表达的影响。结果发现细菌脂多糖（LPS）呈浓度领带性地激活诱导型NOS（iNOS）,促进NO生成。IL－10（10^-10-10^-8g/ml）呈浓度依赖性地上调内皮型NOS（eNOS）蛋白表达及其活性,但对iNOS活性及表达无明显影响,IL－10（10^-9-10^-8g/ml）显著抑制10μg/ml LPS诱导的NO生成和iNOS激活;而高浓度IL－10（10^-7g/ml）则上调iNOS的活性,对eNOS蛋白的表达知活性无明显影响。因此IL－10对NO／NOS系统具有双重影响,一方面可抑制炎症介质诱发的作为炎性物质的iNOS的表达及激活,另一方面可上调内皮源扩血管物质NO的释放。