Archives internationales de pharmacodynamie et de therapie最新文献

The combination of lipopolysaccharide (LPS; 100 ng/ml) and interferon-gamma (IFN-gamma; 10 IU/ml) synergistically stimulated induction of nitric oxide synthase activity in J774 macrophages, measured by nitrite accumulation during an overnight incubation. Neither the phorbol ester, phorbol 12-myristate 13-acetate (PMA; 10(-9) - 3 x 10(-6) M) nor the calcium ionophore, A23187 (10(-7) - 10(-4) M), alone or in combination, stimulated accumulation of nitrite. They were also unable to substitute for IFN-gamma in priming J774 macrophages to stimulation with LPS. Phorbol 12-myristate 13-acetate (10(-9) - 3 x 10(-6) M) produced a concentration-dependent inhibition of nitrite accumulation when added prior to stimulation with LPS and IFN-gamma, but enhanced nitrite accumulation when added 12 hours following stimulation with LPS and IFN-gamma. Of the protein kinase C inhibitors tested, staurosporine (10(-9) - 3 x 10(-6) M) and Ro 31-8220 (3 x 10(-9) - 10(-5) M) produced a powerful, concentration-dependent inhibition of nitrite accumulation when added prior to stimulation with LPS and IFN-gamma, but had only slight inhibitory effects when added 12 hours after stimulation with LPS and IFN-gamma. Chelerythrine chloride ( 10(-8) - 3 x 10(-5) M) produced only a slight inhibition of nitrite accumulation when added prior to stimulation with LPS and IFN-gamma, but slightly enhanced nitrite accumulation when added 12 hours following stimulation with LPS and IFN-gamma. The tyrosine kinase inhibitors, genistein (10(-7) - 10(-4) M) and herbimycin A (5.2 x 10(-9) - 1.74 x 10(-6) M), produced a powerful concentration-dependent inhibition of nitrite accumulation when added prior to stimulation with LPS and IFN-gamma. In contrast, herbimycin A had only a slight inhibitory effect when added 12 hours following stimulation with LPS and IFN-gamma, and genistein had no effect. When used in combination prior to stimulation with LPS and IFN-gamma, herbimycin A (1.7 x 10(-7) M) and staurosporine (3 x 10(-8) M) produced additive inhibitory effects on nitrite accumulation, but herbimycin A, together with Ro 31-8220 (3 x 10(-6) M) or chelerythrine chloride (10(-5) M), produced no further effects. These results provide strong evidence for the involvement of tyrosine kinases in the induction of nitric oxide synthase by LPS and IFN-gamma in J774 macrophages. They also suggest a role for protein kinase C, but elucidation of the precise mechanisms by which this pathway interacts with tyrosine kinase to regulate the expression of nitric oxide synthase requires further investigation.

A simple and reproducible canine model of platelet-rich coronary artery thrombosis, suitable for the evaluation of antithrombotic drugs, has been developed. In this model, thrombus was initiated in the left arterial descending coronary artery by means of transmural green light (540 nm) in the presence of i.v. administered rose bengal (a photosensitizer dye). The photochemical reaction between green light and rose bengal causes endothelial injury which is followed by platelet adhesion aggregation and formation of an occlusive platelet-rich thrombus at the site of the photochemical reaction. In 9 out of 12 animals, occlusion of the coronary artery occurred within 60 min after irradiation with green light and infusion of rose bengal. Infusion of tissue-type plasminogen activator (50,000 IU/kg) produced thrombolysis in 6 out of 9 animals within 60 min. Reocclusion was observed in 4 of these 6 animals. Photochemically induced thrombosis in the canine coronary artery provides a simple and platelet-rich thrombosis model suitable for the evaluation of antithrombotic and thrombolytic preparations.

The methyl esters of succinic and glutamic acid are currently under investigation as possible tools for stimulation of insulin biosynthesis and release in non-insulin-dependent diabetes mellitus. The present study deals with the secretory response of the pancreatic B-cell to these esters after intraduodenal administration to anaesthetized rats. The dimethyl ester of succinic acid and, to a lesser extent, its monomethyl ester both increased the plasma insulin concentration, whilst the dimethyl ester of glutamic acid virtuality failed to do so. The stimulation of insulin release, caused by the dimethyl ester of succinic acid, was faster and more pronounced than that evoked by an equimolar amount of glucose. The present study thus reveals that the latter ester, when administered via the gastrointestinal tract, evokes a more brisk and more ample secretory response of the pancreatic B-cell than that evoked by glucose.

The effects of the angiotensin-converting enzyme inhibitors, captopril, lisinopril and enalapril-maleate (the latter being a prodrug that has to be converted into enalaprilat), and bradykinin were investigated in the presence or absence of indomethacin and bradykinin receptor antagonists in dog renal arterial rings precontracted with either prostaglandin F2 alpha or phenylephrine. At a high precontraction level (10 microM of prostaglandin F2 alpha), captopril did not relax the arteries. However, when the tension was low (0.5 microM), both captopril and lisinopril produced endothelium-dependent relaxations. The maximum relaxations for captopril and lisinopril were 57 +/- 6% and 64 +/- 15%, respectively. Enalapril-maleate failed to relax the renal arteries even when the vascular tone was low. In endothelium-intact arteries precontracted with phenylephrine (0.2 microM), captopril and lisinopril produced a maximum relaxation of 60 +/- 9% and 29 +/- 5%, respectively, in arteries with intact endothelium, whilst responses to enalapril-maleate were inconsistent. Renal artery rings with rubbed endothelium failed to relax in response to bradykinin or captopril. We observed significant variations in both captopril- and lisinopril-induced endothelium-dependent relaxations in one tenth of the preparations. The relaxations to bradykinin and captopril were not affected by indomethacin (3 microM), whereas they were markedly attenuated by NG-nitro-L-arginine (0.1 mM). The bradykinin-antagonist, N alpha-adamantane-acetyl-D-Arg-(Hyp3, Thi5,8, D-Phe7)BK, or the specific bradykinin2 receptor antagonist, HOE140, completely abolished the relaxation responses to captopril and reduced the potency of bradykinin, but failed to affect the acetylcholine-induced responses. The results suggest that the relaxant effect of captopril is mediated by endogenous bradykinin or by activation of bradykinin receptors. The proposed mechanisms by which captopril relaxes the renal arteries are: (1) inhibition of tissue kininase II, which leads to accumulation of endogenous bradykinin; (2) shift in angiotensin I metabolism towards (a) relaxant angiotensin derivative(s); and (3) interaction with bradykinin receptors.

The effect of K-7259, a novel derivative of dilazep, on the cardiovascular action of adenosine was studied in the aortic ring and isolated perfused heart in guinea-pigs, and compared with that of dilazep. Adenosine produced a concentration-dependent relaxation in phenylephrine (2 x 10(-6) M)-contracted aortic rings and exhibited a negative chronotropic effect in the isolated perfused heart. Dilazep (10(-8), 10(-7) and 10(-6) M) potentiated significantly the relaxing action of adenosine on the aortic ring in a concentration-dependent way. K-7259 (10(-6) M), however, did not potentiate the relaxing action of adenosine, although the high concentration of K-7259 (10(-5) M) potentiated it slightly but significantly. The negative chronotropic effect of adenosine was also potentiated by dilazep (10(-7) and 10(-6) M), but not by K-7259 (10(-6) M). These results suggest that the potentiating action of K-7259 on the cardiovascular effects of adenosine is very weak when compared with that of dilazep.

The antagonism of depolarizing blockers, principally succinylcholine and decamethonium, by tetraethyl- and tetrabutylammonium ions in an in vivo neuromuscular preparation in anesthetized cats is described; possible mechanisms for these effects are discussed. Tetraethyl- (50-100 mg/kg, i.v.) and tetrabutylammonium (1-5 mg/kg, i.v.) produced sharp reversals of 95-99% succinylcholine and decamethonium blocks. These reversals were effective and sustained at any point during the course of the blockades. Tetraethyl- or tetrabutylammonium, administered 2-3 min before succinylcholine or decamethonium, prevented blockade, an effect compatible with an earlier reported in vitro investigation. The studies of others disclose the interaction of depolarizing blockers with acetylcholine receptors, leading to channel opening, channel entry and binding therein of these blockers. The present studies support this in showing the prevention of succinylcholine and decamethonium block by the prior administration of tetraethylammonium, which also interacts with acetylcholine receptors. It is proposed that a possible mechanism for tetraethylammonium reversals of succinylcholine and decamethonium blocks may be attributable to the tetraethylammonium reversal of a K+ current block by quaternary ammonium ions such as succinylcholine and decamethonium. Tetraethyl- and tetrabutylammonium ions proved to be effective antagonists of succinylcholine block following inactivation of plasma cholinesterases by hexafluorenium.

The present study was undertaken to determine whether N-(2-mercaptopropionyl)-glycine, a membrane-permeable antioxidant agent, improves the ischemia/reperfusion-induced cardiac contractile dysfunction. Rat isolated hearts were subjected to a 35 min global ischemia, followed by a 60 min reperfusion. Ischemia/reperfusion did not result in the recovery of postischemic left ventricular developed pressure. Reperfusion markedly increased the content of the thiobarbiturate-reacting substance in the myocardium. Treatment of the perfused heart with 1 mM of N-(2-mercaptopropionyl)-glycine, either during a 30 min pre-ischemia or during a 30 min pre-ischemia and the first 10 min of reperfusion, resulted in an appreciable recovery of the postischemic left ventricular developed pressure and an attenuation of the increase in thiobarbiturate-reacting substance content. When hearts were treated with the same concentration of the agent only during the first 10 min of reperfusion, the cardiac contractile function was not improved during reperfusion despite the increase in thiobarbiturate-reacting substance content of the reperfused myocardium. These results suggest that the increase in thiobarbiturate-reacting substance content during reperfusion is independent of the postischemic contractile failure.

This investigation was performed to determine whether droperidol interacts with 5-hydroxytryptamine (serotonin) receptors in the rat aorta. Droperidol caused concentration-dependent vasorelaxation in endothelium-intact and endothelium-denuded aortic rings precontracted with noradrenaline or 5-hydroxytryptamine. Conversely, the contractile effect of prostaglandin F2 alpha was not affected by droperidol. Pretreatment with propranolol, brompheniramine and atropine (10(-6) M each) did not alter the relaxant effects of droperidol. In addition, droperidol shifted the 5-hydroxytryptamine and noradrenaline concentration-response curves to the right in an apparently competitive manner. However, prazosin did not modify the concentration-response curve to 5-hydroxytryptamine, which is consistent with the hypothesis that the latter has an intrinsic efficacy for non-alpha 1-adrenoceptors. These results strongly suggest that a direct arterial endothelium-independent relaxant action of droperidol can be attributed to a 5-hydroxytryptamine receptor-blocking property and support its vascular alpha-adrenoceptor-blocking effect.

The contractile response to a protein kinase C activator, phorbol 12,13-dibutylate, and the relaxant effect of nicorandil on this contraction were studied in the canine isolated coronary artery. Phorbol 12,13-dibutylate (10(-9)-3 x 10(-6) M) elicited slowly developing, dose-dependent and sustained contractions which were antagonized by a putative protein kinase C inhibitor, staurosporine. Removal of Ca2+ from the medium or pretreatment with nifedipine (10(-6) M) partly inhibited the response to phorbol 12,13-dibutylate. Nicorandil (10(-7)-3 x 10(-4) M) produced full relaxation at its maximum effect in rings precontracted with phorbol 12,13-dibutylate (10(-7) M). Nitroglycerin (10(-9)-3 x 10(-5) M) caused only a partial relaxation (to about 30%), but subsequent addition of cromakalim (10(-5) M) to the nitroglycerin-treated rings (cromakalim alone inducing a partial relaxation of about 35%) caused nearly full relaxation. Methylene blue (5 x 10(-6) M) inhibited the relaxant response to lower (< or = 10(-5) M) but not to higher concentrations of nicorandil, while it antagonized the nitroglycerin-induced relaxation at all concentrations used. The relaxant response at higher concentrations of nicorandil (> or = 3 x 10(-5) M) was antagonized by 10(-6) M of glibenclamide. These results suggest that the contraction induced by phorbol 12,13-dibutylate may be related to an activation of protein kinase C and, in part, to increases in the Ca2+ influx via voltage-dependent Ca2+ channels. It appears that nicorandil relaxes the contraction induced by phorbol 12,13-dibutylate through a nitrate-like mode of action, combined with a potassium channel-opening activity.

We investigated the effects of various anticholinergic drugs (atropine, oxybutynin, terodiline and propiverine) on the contractions induced by acetylcholine, KCl, CaCl2, and electrical field stimulation, in human isolated urinary bladder smooth muscles using the muscle bath technique. Urinary bladders were obtained from 20 patients who underwent total cystectomy due to malignant bladder tumor. The detrusor preparations were taken from the intact part of the dome of the bladder. Acetylcholine caused a concentration-dependent contraction in human detrusor preparations. Atropine (10(-9)-10(-6) M), oxybutynin (10(-8)-10(-5) M), terodiline (10(-7)-10(-5) M) and propiverine (10(-7)-10(-5) M) caused parallel shifts to the right of the concentration-response curves to acetylcholine. The rank order of pA2 values was: atropine > oxybutynin > terodiline = propiverine. Atropine did not suppress the maximum contraction to acetylcholine, while the other drugs significantly suppressed the maximum contractions at the higher concentrations. Each drug caused a concentration-dependent inhibition of the KCl (80 mM)- and CaCl2 (5 mM)-induced contractions; the maximum inhibitions of terodiline and propiverine were significantly greater than those of oxybutynin and atropine. Each drug caused a concentration-dependent inhibition of the contraction induced by electrical field stimulation; the maximum inhibitions of terodiline and propiverine were significantly greater than those of oxybutynin and atropine. The results suggest that the drugs have both anticholinergic and calcium antagonistic effects. Furthermore, it also appears that part of the human bladder contraction, which was significantly inhibited by terodiline and propiverine, is an atropine-resistant component.