内皮素-1对大鼠血管平滑肌的作用及川芎嗪的对抗效果

用离体大鼠的主动脉和培养的大鼠胸主动脉平滑肌细胞,研究了内皮素-1对主动脉的收缩作用及对主动脉平滑肌细胞增殖周期及能量代谢的影响,结果表明1.0～18.0nmol·L~1的内皮素-1能引起浓度依赖性血管收缩,川芎嗪能有效对抗内皮素-1血管收缩作用.100～100.0 pmol·L~1的内皮素-1能使S+G_2+M期细胞的比例增加,具有促进血管平滑肌细胞增殖的作用;10.0 pmol·L~1内皮素-1作用10 min可升高平滑肌细胞ATP含量,20 min之后ATP含量一直低于正常水平,内皮素1对平滑肌细胞ATP含量的影响呈双相作用,先升高后降低     

Biphenylcarboxamide derivatives as antagonists of platelet-activating factor

A series of N-[4-(3-pyridinyl)butyl]-1,1'-biphenyl-4-carboxamides was prepared, and the compounds were evaluated for platelet-activating factor (PAF) antagonist activity in a binding assay employing washed, whole dog platelets and in vivo for their ability to inhibit PAF-induced bronchoconstriction in the guinea pig. The inclusion of a methyl group in the R configuration on the side-chain carbon adjacent to the carboxamide nitrogen atom of these derivatives resulted in a marked enhancement of potency in the binding assay for compounds unsubstituted in the biphenyl 2-position and, more importantly, in improved oral bioavailability. Previous work with related pyrido[2,1-b]-quinazoline-8-carboxamides suggests that the presence of such an alkyl group improves bioavailability by rendering the resulting compounds resistant to degradation by liver amidases. The most interesting compounds to emerge from this work are (R)-2-bromo-3',4'-dimethoxy-N-[1-methyl-4-(3-pyridinyl)butyl]-1,1'-bi phe nyl- 4-carboxamide (33) and (R)-2-butyl-3',4'-dimethoxy-N-[1-methyl-4-(3-pyridinyl)butyl]- 1,1'-biphenyl-4-carboxamide (40) each of which inhibits PAF-induced bronchoconstriction in the guinea pig by greater than 55%. 6 h after an oral dose of 50 mg/kg.     

Structure-activity relationships in platelet-activating factor. 12. Synthesis and biological evaluation of platelet-activating factor antagonists with anti-HIV-1 activity

The HIV-1 central nervous system infection leads to the onset of neurological impairments called AIDS dementia complex (ADC). PAF plays an important role in this pathology, as it is an HIV-1-induced neurotoxin produced by infected or activated macrophages and microglia, in the brain. We previously reported that PAF-antagonists bearing a trisubstituted piperazine presented in vitro anti-HIV-1 activity in human macrophages. To improve the pharmacological activities of our lead compound, 1a, we modified its carbamate function and evaluated both its antiretroviral and anti-PAF activities. One carbamate derivative (10c) demonstrated a similar antiviral activity but a higher anti-PAF potency, whereas 4a, with an ureide function, presents an increased antiviral activity and can be considered as a pure antiretroviral drug, as it does not present PAF-antagonism. Moreover, we measured the ability of 1a to cross the blood-brain barrier, using the in situ mouse brain perfusion method and its plasmatic concentrations after iv and po administration. The transport parameter measured (K(in)) proves that 1a is able to cross this biological barrier, but a pharmacokinetic study reveals its weak bioavailability in rats.     

Differential actions of platelet-activating factor (PAF) receptor antagonists on the vasodilator and vasoconstrictor effects of PAF in the rat perfused heart.

Selectivity for blocking the coronary vasodilator and vasoconstrictor effects of platelet-activating factor (PAF) in the rat perfused heart was observed with different PAF antagonists. CV-6209 showed selectivity for blocking the vasodilator effect of PAF and a higher concentration (10 fold) was required to block the vasoconstrictor effect. The remaining PAF antagonists (FR-900452, WEB 2086 and BN-50739) showed selectivity for blocking the vasoconstrictor effect of PAF (10, 200 and 1000 fold respectively). A combination of low concentrations of CV-6209 (10 nM) with FR-900452 (5 microM) or WEB 2086 (0.5 microM) was effective in blocking both the vasodilator and vasoconstrictor effects of PAF. CV-6209 and WEB 2086 did not affect the vasodilator action of leukotriene B4 (LTB4) and the vasoconstrictor action of LTC4 and LTD4. Our results support the hypothesis that the functionally opposite effects of PAF in the rat perfused heart may be mediated by different PAF receptor subtypes.     

Antagonism of vasoconstriction induced by platelet-activating factor in guinea-pig perfused hearts by selective platelet-activating factor receptor antagonists.

Platelet-activating factor (Paf) is a potent coronary vasoconstrictor in rat, guinea-pig, dog and pig. The present study investigated the mechanism and duration of Paf in guinea-pig isolated, Krebs-perfused hearts. Dose-related and sustained decreases in cardiac contractility and increases in coronary perfusion pressure were elicited by bolus doses of Paf (0.3-100 pmol). Platelet-activating factor (30 pmol) induced increases in the production of immunoreactive thromboxane B2 (TXB2), leukotriene B4 (LTB4) and LTC4, but not 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha). In addition, the release of leukotriene-like material following Paf was observed using on-line superfusion bioassay. The coronary vasoconstrictor actions of Paf were partially antagonized by the leukotriene receptor antagonist, FPL 55712 (1.9 microM), or by indomethacin (2.8 microM). The combined use of these compounds did not result in further significant inhibition. The Paf receptor antagonists, BN 52021 (30 microM) and L 652, 731 (10 microM), antagonized both the increase in coronary perfusion pressure and the decrease in cardiac contractility induced by Paf (10-100 pmol) in a surmountable and relatively selective manner. The effects of a bolus dose of 100 pmol Paf were sustained in excess of 18 min. Exogenous Paf underwent little metabolism on passing through the coronary circulation with only 2% being converted to lyso-Paf and approximately 4% being retained by the heart after 18 min of perfusion. These results suggest that the coronary vasoconstrictor actions of Paf are partially dependent on the release of vasoactive arachidonic acid metabolites. The extraordinary potency and the long-lasting action of Paf indicate a potential role for this pro-inflammatory mediator in disorders of the coronary circulation.     

The action of prostanoid receptor agonists and antagonists on smooth muscle and platelets.

1. Prostanoid receptors have been characterized in a range of guinea-pig and rat smooth muscle and platelets, according to the scheme of Coleman et al., (1985a), using agonists (prostaglandin D2 (PGD2), PGE1, PGE2, 16,16 dimethyl PGE2, PGF2 alpha, PGI2 and U46619) and putative selective antagonists (AH 6809 and SQ 29,548). 2. The ileum possesses EP1- and IP-receptors; the trachea, EP1-EP2- and TP-receptors; the oesophageal muscularis mucosa, EP1- and TP-receptors; the aorta and the portal vein TP-receptors. The rat colon possesses IP-, FP- and TP-receptors. 3. Guinea-pig platelets possess both IP and DP receptors mediating an inhibition of aggregation and TP receptors mediating proaggregation responses. No evidence was found for the presence of EP1-, EP2- or FP-receptors. 4. Misoprostol and fenprostalene were characterized using the above preparations. Misoprostol acts as a selective EP1-agonist, and has little or no DP, FP, IP and TP activity. In the trachea precontracted with carbachol no evidence of EP2-receptor stimulation was observed. Fenprostalene possesses FP and TP activity but no EP1, EP2, DP or IP activity.     

Difference in mode of action of alpha 1-adrenoceptor antagonists on some vascular smooth muscles and efficacy

Effect of YM-12617, a selective and potent alpha 1-adrenoceptor antagonist on dose-response curves of alpha 1-adrenoceptor agonists, norepinephrine, phenylephrine and naphazoline, was tested in isolated rabbit vascular smooth muscles such as the femoral vein, portal vein and aorta. YM-12617 shifted the dose-response curves for norepinephrine and phenylephrine to the right and also declined the maximum response in the femoral vein, where norepinephrine and phenylephrine behaved as low efficacy agonists. Similar results were obtained on the curve of naphazoline in the portal vein, where the efficacy of naphazoline was low. However, the efficacies of norepinephrine, phenylephrine and naphazoline were high in the aorta. The dose-response curves for three alpha 1-agonists were shifted by YM-12617 in a parallel manner in the aorta. The curves of norepinephrine and phenylephrine were also shifted by YM-12617 in the portal vein, where the efficacies of both the alpha 1-agonists were high. The present results suggest that the mode of antagonism between the alpha 1-agonist and alpha 1-antagonist is dependent on the efficacy of the alpha 1-agonist which depends upon the receptor-density in the organ used.     

Ocular actions of platelet-activating factor: clinical implications

Introduction: To summarize the currently available evidence of platelet-activating factor (PAF) implication in the pathogenesis of inflammatory ocular diseases.

Areas covered: PAF is a potent mediator of inflammation, implicated in the pathogenesis of chronic inflammatory disorders, allergic reactions, oncogenic transformation, wound repair and hypoxia-induced angiogenesis. It seems to be involved in the protection of ocular surface against various harmful agents through inflammatory processes, which can lead to chronic allergic reactions or even corneal neovascularization and haze, if they do not undergo regulation. Pathogenesis of uveitis, which is significant cause for the blurring of the visual system, has also been associated with PAF's activity. The hypoxia and the breakdown of the blood–retina barrier, observed in severe vascular retinal diseases, such as age-related macular degeneration and diabetic retinopathy, are associated with PAF ocular activity.

Expert opinion: Understanding the pathophysiology of vision threatening diseases could enhance clinical treatment and encourage experimental studies, which could be based on potential beneficial effects of new agents, such as PAF antagonists.     

Pentadienyl carboxamide derivatives as antagonists of platelet-activating factor

A series of N-[4-(3-pyridinyl)butyl]-5,5-disubstituted-pentadienamides was prepared and evaluated for PAF-antagonist activity. Compounds were assayed in vitro in a PAF-binding assay employing washed, whole dog platelets as the receptor source and in vivo after intravenous or oral administration for their ability to prevent PAF-induced bronchoconstriction in guinea pigs. Criteria required for good oral activity in the latter model include an (E,-E)-5-phenyl-2,4-pentadienamide, a second phenyl or a four- or five-carbon alkyl moiety in the 5-position of the diene, and an (R)-[1-alkyl-4-(3-pyridinyl)butyl] substituent on the carboxamide nitrogen atom. The alkyl substituent on this side chain can be methyl, ethyl, or cyclopropyl. Two members of this series, [R-(E)]-5,5-bis(4-methoxy-phenyl)-N- [1-methyl-4-(3-pyridinyl)butyl]- 2,4-pentadienamide (31) and [R-(E,E)]-5-(4-methoxyphenyl)-N-[1-methyl-4- (3-pyridinyl)butyl]-2,4-decadienamide (58), were selected for further pharmacological evaluation. Both were found to be substantially longer acting after oral administration than the corresponding S enantiomers in the guinea pig bronchoconstriction assay. A second in vivo model used to evaluate PAF antagonists determines the ability of test compounds to decrease the area of skin wheals induced by an intradermal injection of PAF. In this model, using both rats and guinea pigs, compounds 31 and 58 were found to be as active as the reference PAF antagonist 3-[4-(2-chlorophenyl)-9-methyl-6H- 1-(4-morpholinyl)-1-propanone (45).     

Inhibition of platelet-activating factor synthesis in human neutrophils and platelets by propionyl-L-carnitine.

Propionyl-L-carnitine (PrC) has been shown to exert beneficial effects in the treatment of myocardial and peripheral ischemia in man. These conditions are associated with the activation of circulating neutrophils and platelets. To determine whether PrC could affect the synthesis of lipid mediators known to influence neutrophil and platelet functions, we explored the effects of PrC on the synthesis of platelet-activating factor (PAF) and arachidonic acid (AA) metabolites. Preincubation (90 min) of human neutrophils with PrC (0.1-100 microM) inhibited the synthesis of PAF and of a PAF analog (1-alkyl-1'enyl-2-acetyl-sn-glycero-3-phosphoethanolamine: AEGPE) induced in vitro by the calcium ionophore A23187. In contrast, concentrations of PrC up to 100 microM did not influence the uptake of exogenous AA or the A23187-induced release of AA and eicosanoids from neutrophils in vitro. PrC (1 microM) also inhibited PAF synthesis from human platelets stimulated in vitro with thrombin, but had no effect on thrombin-induced aggregation. Oral administration of PrC (2 g/day for two weeks) to five normal volunteers resulted in a significant inhibition of PAF and AEGPE synthesis by neutrophils stimulated with A23187 ex vivo, with no effect on AA or eicosanoid release. These data indicate that PrC selectively inhibits in vitro and ex vivo PAF synthesis from human neutrophils and platelets without influencing AA metabolism or eicosanoid release. This effect of PrC might represent an additional mechanism by which this molecule can exert protective effects in tissue ischemia and in other inflammatory diseases associated with neutrophil and platelet activation.     

Relaxation effects of matrine on guinea-pig aortic smooth muscles

Objective The present in vivo study was undertaken to determine whether matrine,a kind of traditional Chinese medicinal alkaloid,would relax the isolated guinea pig aortic smooth muscles,if so,to investigate the mechanism involved.Methods The concentration-dependent relaxation response to matrine was studied in phenylephrine or potassium chloride precontracted guinea pig aortic rings.Results Matrine(1×10-4 M-3.3×10-3 M)relaxed the endothelium denuded aortic rings precontracted submaximally with phenylephrine,in a concentration-dependent manner,and it's preincubation(3.3×10-3 M)produced a significant rightward shift in the phenylephrine dose-response curve,but had no effects on the potassium chloride-induced contraction.The anticontractile effect of matrine was not reduced by the highly selective ATP-dependent K+ channel blocker glibenclamide(10-5 M),the non-selective K+ channel blocker tetraethylammonium(10-3 M),as well as the β-antagonist propranolol(10-5 M).In either "normal" or "Ca2+-free" bathing medium,the phenylephrine-induced contraction was attenuated by matrine(3.3×10-3 M),indicating the vasorelaxation was due to inhibit of intracellular and extracellular Ca2+ mobilization.Conclusions The results obtained clearly demonstrated that matrine inhibits phenylephrine-induced contractions by inhibiting activation of α-adrenoceptor and interfering with both the release of intracellular Ca2+ and the influx of extracellular Ca2+.     

The actions of Paf-acether (platelet-activating factor) on guinea-pig isolated heart preparations.

Paf-acether (platelet-activating factor) is a phospholipid capable of stimulating platelets to release their granular contents and cause platelet aggregation. When Paf-acether was administered to isolated heart preparations from normal guinea-pigs there was a significant concentration-dependent reduction in coronary flow and contractile force. The high concentration of Paf-acether was equally effective in reducing these cardiac parameters in the presence of atropine. The non-acetylated Paf-acether analogue, 2-lyso Paf-acether, the enantiomer, and a closely related phospholipid 1, alpha-lysophosphatidylcholine palmitoyl, did not affect coronary flow and contractile force, indicating the specificity of Paf-acether. These data demonstrate a potent effect of Paf-acether on cardiac function. Whether or not these effects are direct or mediated through generation of endogenous mediators remains to be established.     

Characterization of receptors for platelet-activating factor on platelets, polymorphonuclear leukocytes and macrophages

1. We have compared the potency of the putative platelet-activating factor (Paf) receptor antagonists (WEB 2086, L-652,731 and BN 52021) against Paf-induced aggregation of rabbit and guinea-pig platelets, aggregation of rabbit polymorphonuclear leukocytes (PMNLs) and prostacyclin generation by guinea-pig resident peritoneal macrophages. 2. On rabbit washed platelets and PMNLs WEB 2086, L-652,731 and BN 52021 each antagonized competitively Paf-induced aggregation. The rank order of potency was WEB 2086 congruent to L-652,731 greater than BN 52021 and was the same for the two cell types. 3. The pA2 values for each of the three antagonists were similar on rabbit washed platelets and PMNLs. Moreover, the pA2 for WEB 2086 on rabbit platelets (7.58) did not differ significantly from that on guinea-pig platelets (7.69). 4. On guinea-pig resident peritoneal macrophages WEB 2086 was 10 fold less potent for receptors mediating increased generation of 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha) than for those mediating platelet aggregation. 5. The potencies of L-652,731 and BN 52021 were also markedly less (2 log units) for the macrophage receptors than for platelet or PMNL receptors and BN 52021 was more potent than L-652,731 in the macrophages. 6. WEB 2086 and L-652,731 significantly reduced basal 6-oxo-PGF1 alpha produced by macrophages, but none of the antagonists affected 6-oxo-PGF1 alpha production during stimulation by A23187. 7. These data raise the possibility that there may be a Paf receptor-subtype mediating prostacyclin generation in macrophages that is different from that on the platelet and PMNL.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thienotriazolodiazepines as platelet-activating factor antagonists. Steric limitations for the substituent in position 2

The preparations of thienotriazolodiazepines bearing a substituted ethynyl group at the 2-position, and the corresponding cis-olefins and fully saturated analogues are described. The compounds were evaluated as potential antagonists of platelet-activating factor (PAF) in in vitro and in vitro test models. The new thienotriazolodiazepines are compared with known related compounds such as WEB 2086 (compound 6) and the phenylethyl derivatives 27 and 28.     

The actions of some vasoactive polypeptides and their antagonists on the anococcygeus muscle

1 The action of three polypeptides, bradykinin, substance P and eledoisin known to inhibit vascular smooth muscle has been examined on the anococcygeus muscle of the rat, cat and rabbit.2 In the atonic rat muscle, bradykinin and substance P had little or no effect on tone but eledoisin produced a sustained dose-related contraction which could be abolished by phentolamine (1 muM) and is, therefore, probably an indirect sympathomimetic effect. On the motor response to field stimulation of adrenergic nerves, bradykinin had no effect whereas both substance P and eledoisin reduced this response. The mechanism of action was further analysed with eledoisin by examining its effect on the response to noradrenaline. Eledoisin did not alter the dose-response curve to noradrenaline and its inhibitory action is likely, therefore, to be presynaptic.3 In the rat anococcygeus muscle in which the tone was raised by guanethidine or carbachol, bradykinin and substance P reduced this tone whereas eledoisin continued to exert a motor action. Compared with substance P the inhibitory effect of bradykinin appeared at lower concentrations (threshold 0.01 mug/ml), developed more rapidly and the size of the response was greater.4 The effect of bradykinin on the tonically contracted cat and rabbit anococcygeus muscles was examined in addition to that of the rat. In all three species bradykinin caused inhibition and the magnitude of the response was equal to the maximum effect of inhibitory nerve stimulation. None of the peptides affected the inhibitory response to nerve stimulation itself.5 The effects of three substances, hesperitin, khellin and apiin, reported in other tissues to antagonize the action of bradykinin were examined both on the inhibitory response to bradykinin and to field stimulation. None of them was able to inhibit either response, although they reduced tone when given by themselves. During these experiments it was found that ethanol antagonized the inhibitory response to field stimulation.6 The possibility that bradykinin or some related peptide might play a part in the inhibitory response to nerve stimulation in the anococcygeus is discussed.     

Pharmacological actions of tannic Acid. I. Effects on isolated smooth and cardiac muscles and on blood pressure.

Tannins are common constituents of medicinal plant crude extracts and have been reported to have pharmacological actions of their own. Studies on these actions are likely to be helpful in interpreting data obtained with tannin-rich crude plant extracts. In this context, the present report analyses the effects of tannic acid on responses of the isolated rat uterus and vas deferens to agonists and left atrium to electrical stimulation, as well as on blood pressure in anesthetized rats. Tannic acid dose-dependently and non-competitively antagonized contractions to different agonists in rat uterus and vas deferens. The compound produced a biphasic effect in the atrium. Whereas lower concentrations (30 to 100 microg/ml) enhanced inotropism, higher concentrations (> 300 microg/ml) promoted depression of contractility. Intravenous tannic acid led to hypotension, which was partially reduced by antihistamine pretreatment, but did not affect heart rate. The depressant effect of tannic acid in uterine fragments was potentiated by increasing calcium concentration in the bathing solution, although in the depolarized strips the compound non-competitively antagonized calcium-induced contractions. The results suggest that tannic acid can affect calcium availability for contraction of smooth and cardiac muscles. This action could well mask the effects of other active constituents of tannic-rich plant extracts.     

Magnesium as a relaxing factor of airway smooth muscles.

In the search for effective treatment of a life-threatening asthma attack, intravenous magnesium infusion has been studied in asthmatic patients because of its potential effect to reverse bronchospasm and improve pulmonary function. To determine whether magnesium sulfate inhibits airway smooth muscle contraction and the possible mechanism of its action, in vitro experiments were performed on rabbit tracheas. Tracheal muscle strips were obtained from 12 rabbits. Initially, the muscle strip was pretreated with a solution containing MgSO4 (concentrations 10(-4) to 2 M) and 85 mM KCl. The response curve of the muscle was recorded. Application of the above solution led to a 40% relaxation at a magnesium concentration of 10(-1) M. The time to peak and to wash-out remained unchanged, and fixed to 66.6 and 123.3 sec, respectively, not influenced by magnesium concentration. On a second phase, the muscle strip was pretreated with KCl alone, and only after a full contractile response was obtained did we add 10(-1) M MgSO4, which led to full relaxation. We follow the same protocol using 10(-4) M acetylcholine (ACH). In this case, simultaneous application of 10(-1) M MgSO4 caused a 55.1% decrease in muscle contraction and a 60% decrease in time to peak. On a second phase, we added magnesium as we did with KCl, but without the same result. Magnesium caused a full relaxation when the constrictor agent was KCl, but a residual contraction was observed when the constrictor was ACH. Based on the knowledge that ACH and KCl cause Ca2+ influx into the cells and subsequent contraction by acting on different Ca2+ channels, we concluded that magnesium inhibits Ca2+ influx by blocking the voltage-dependent calcium channels.