Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cardiac in vitro effects of R 80122, a novel phosphodiesterase (PDE) inhibitor, were investigated and compared with those of the reference compound milrinone and of the calcium-sensitizer adibendan. In guinea pig left atria, both milrinone and R 80122 increased contractile force; 10 microM milrinone was equieffective to 1 microM R 80122. The rate of spontaneously beating atria was not altered by R 80122 in the concentration range of 0.01-0.3 microM. Higher concentrations (1-10 microM) led to a statistically insignificant increase of 20%. Milrinone's effect on frequency was more pronounced and amounted to 21% at 10 microM and to 40% at 100 microM. Adibendan increased heart rate (HR) by 10% at a concentration of only 0.03 microM. This effect was not enhanced any further by increasing the concentration. In papillary muscle, the positive inotropic effects of both milrinone and R 80122 were inhibited by carbachol, indicating involvement of cyclic AMP. Further indications for a cyclic AMP-dependent action were obtained by induction of slow action potentials and synergism with isoprenaline. In electrophysiologic measurements, milrinone reduced action potential duration (APD) in a high concentration whereas R 80122 had no effect. Action potential changes elicited by a toxic concentration of ouabain were reduced by R 80122. Relaxation of rat aortic rings contracted by KCl and relaxation of guinea pig aortic rings contracted by norepinephrine (NE) was comparable for both milrinone and R 80122. R 80122 also caused relaxation of canine coronary arteries constricted with prostaglandin F2 alpha (PGF2 alpha) both with and without endothelium. NE-induced contractions in canine gastrosplenic arteries were not affected by R 80122. Cardiac contractility that had been impaired to various degrees by pentobarbital or by aging was restored to control values by both milrinone and R 80122. R 80122 enhanced cardiac contractility at lower concentrations than milrinone with no concomitant increase in frequency or shortening of the action potential, which may be advantageous for treatment of heart failure.
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PMID:In vitro pharmacology of R 80122, a novel phosphodiesterase inhibitor. 128 Jul 31

The effect of a new cardiotonic agent Y-20487 [6-(3,6-dihydro-2-oxo-2H-1,3,4-thiadiazin-5-yl)-3,4-dihydro-2(1H)- quinolinone] on cyclic AMP levels of rat ventricular cardiomyocytes and the contractile force of papillary muscles was investigated in comparison with selective cyclic AMP phosphodiesterase (PDE) inhibitors, milrinone (PDE-III selective), rolipram and Ro 20-1724 (PDE-IV selective), and a nonselective inhibitor 3-isobutyl-1-methylxanthine (IBMX). Rolipram and Ro 20-1724 did not elicit cyclic AMP accumulation and positive inotropy, but they potentiated the isoproterenol (ISO)-induced cyclic AMP accumulation more effectively than IBMX. Rolipram was more effective than Ro 20-1724 in enhancing ISO-induced cyclic AMP accumulation but was less effective in enhancing the ISO-induced positive inotropic effect, indicating that these agents produce a differential action on cyclic AMP metabolism and inotropy. Milrinone and Y-20487 elicited cyclic AMP accumulation and positive inotropy by themselves. Whereas milrinone scarcely affected the ISO-induced effects, Y-20487 shifted the concentration-response curve for the positive inotropic effect of ISO to the left to the same extent that IBMX did. Y-20487, however, was much less effective than IBMX in enhancing the ISO-induced cyclic AMP accumulation. The present results indicate that in rat ventricular myocardium, PDE-IV may play a crucial role in breakdown of cyclic AMP generated by beta-adrenoceptor stimulation, whereas other types of PDE isoenzymes, including PDE-III, may be responsible for the cyclic AMP accumulation and direct positive inotropic effect induced by PDE inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of a cardiotonic quinolinone derivative Y-20487 on the isoproterenol-induced positive inotropic action and cyclic AMP accumulation in rat ventricular myocardium: comparison with rolipram, Ro 20-1724, milrinone, and isobutylmethylxanthine. 128 Jul 32

1. Effects of cyclic GMP on the catecholamine-induced chloride current (ICl) were studied using the whole-cell patch-clamp technique combined with internal perfusion in single ventricular myocytes dispersed from guinea-pig heart. 2. When ICl was activated by submaximal doses of isoprenaline (0.01-0.1 microM), adrenaline (0.5-1 microM) and histamine (0.2-0.5 microM), intracellular dialysis with cyclic GMP (10-100 microM) induced an extra increase of ICl. No further increase of ICl was induced by cyclic GMP when ICl was maximally activated. In the absence of agonists, cyclic GMP failed to induce ICl. 3. The enhancement by cyclic GMP was also observed when ICl was activated by external application of 0.2-1.0 microM-forskolin or by internal dialysis with a pipette solution containing 50-200 microM-cyclic AMP. 4. In contrast to cyclic GMP, 10-1000 microM-dibutyryl cyclic GMP and 8-bromo-cyclic GMP were ineffective in modifying ICl. 5. Milrinone (1-10 microM), a specific inhibitor of a kind of phosphodiesterase which is inhibited by cyclic GMP, also enhanced ICl activated by submaximal doses of isoprenaline. Milrinone itself did not activate ICl. 6. When ICl was enhanced by 5 microM-milrinone, an additional application of cyclic GMP failed to increase ICl. In the presence of cyclic GMP, milrinone failed to enhance ICl. 7. The above findings on ICl are analogous to the enhancement by cyclic GMP of the beta-adrenergic stimulation of the Ca2+ current reported in the same preparation, and support the hypothesis that in mammalian cardiac cells cyclic GMP potentiates elevation of cyclic AMP induced by beta-adrenergic agents, and thereby increases the amplitudes of ionic currents.
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PMID:Synergistic action of cyclic GMP on catecholamine-induced chloride current in guinea-pig ventricular cells. 128 6

To evaluate the effects of milrinone (MIL) on hemodynamics and lung water content, we used 10 mongrel dogs with pulmonary hypertension (PH). To induce pulmonary hypertension, we administered two injections of glass beads stirred in saline to dogs. Mean pulmonary arterial pressure (PAP) and pulmonary vascular resistance significantly increased following induction. Milrinone, which inhibits cyclic AMP phosphodiesterase-(PDE) demonstrated pulmonary vasodilation, indicated a reduction in these two parameters. To clarify the drug mechanism, we measured lung water content as extravascular lung thermal volume (ETVL) using a thermo/sodium double-indicator dilution method. The induction of pulmonary hypertension produced a transient reduction in extravascular lung thermal volume. The parameter remained constant following milrinone administration, whereas the control showed a gradual increase. Of the 10 dogs, five were killed to measure gravimetrically the volume of lung water content as a comparison with extravascular lung thermal volume. We concluded that milrinone produced pulmonary vasodilation which induced a reduction in the transmural capillary pressure gradient according to Starling's hypothesis. This study suggests that the reduction in the transmural pressure gradient induced by milrinone may also prevent the re-elevation in extravascular lung thermal volume. Milrinone increases the cyclic AMP level in the endothelium and in the platelet which may affect either directly or indirectly the permeability of capillary endothelium.
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PMID:Effects of milrinone on lung water content in dogs with acute pulmonary hypertension. 129 25

Four cyclic AMP (cAMP)-phosphodiesterases (PDE) belonging to families I, II, III and IV were identified in homogenates from human failing hearts. On fractionation of cardiac membranes, the cyclic GMP (cGMP)-inhibitable cAMP-PDE III copurified with the sarcoplasmic reticulum. cAMP-PDE activities were separated from the soluble fraction by DEAE-ion exchange chromatography and identified as belonging to the four different families of cAMP-PDEs. Various cAMP-PDE inhibitors, mostly cardiotonic compounds, were tested for their inhibitory potency on the different cAMP-PDEs and their selectivity for the type III isoenzyme was determined. Isobutylmethylxanthine, papaverine, theophylline and dipyridamole inhibited PDE activity in a weak and nonselective manner. Milrinone, enoximone, adibendan, pimobendan, bemoridan and the newly synthesized 1,2,3,5-tetrahydro-2-oxoimidazo[2,1-b]quinazoline derivatives, R 81267 and R 80122 were selective PDE III inhibitors. However, the IC50 values on this enzyme varied from 10 microM for enoximone to 0.036 microM for R 80122. The selectivity of the drugs for PDE III was calculated by division of the IC50 value for PDE I, II or IV by the IC50 value for PDE III. PDE I/PDE III ratio ranged from 95 for enoximone to near 28,000 for R 80122; the PDE II/PDE III ratios ranged from 95 for enoximone to 3,500 for R 80122. Although there was strong variation between the drugs, most of them showed a high selectivity for PDE III in comparison to PDE I and to PDE II. In contrast, PDE IV appeared to be more sensitive to these substances.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of human cardiac cyclic AMP-phosphodiesterases by R 80122, a new selective cyclic AMP-phosphodiesterase III inhibitor: a comparison with other cardiotonic compounds. 132 13

Beta-adrenergic stimulants (Dobutamine and Dopamine) and recently introduced phosphodiesterase inhibitors (PDI) such as Amrinone, Milrinone, Enoximone and Piroximone are the principal inotropic agents for the treatment of acute cardiac failure. Most of the hemodynamic effects of these drugs are comparable, but peripheral vasodilatation is more marked with PDI. A potential advantage of the latter group is the lack of development tolerance, which occurs within 48 to 72 hours after beta-stimulants. On simultaneous administration, additive effects can be observed. Short term clinical results with PDI are good, especially in patients with postoperative cardiocirculatory failure, including cardiogenic shock. In contrast, long-term oral treatment with Amrinone, Milrinone and Enoximone in recent studies was disappointing. Efficacy was not superior to Digoxin, and unwanted side effects were frequent. Intermittent instead of continuous administration of positive inotropic agents should be evaluated in patients with severe congestive heart failure not responding to vasodilators and diuretics.
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PMID:[New positive inotropic drugs in acute and chronic heart failure]. 135 9

Considerable effort and resources have been directed at the development and study of positive inotropic drugs over the past 10-15 years. Much has been learned about the physiology and pharmacology of myocardial contraction, the application of agents to augment contractility, and, importantly, the general and specific limitations of positive inotropic therapy. Studies on acute inotropic intervention have now shown that a drug's ability to augment overall cardiac performance is heavily dependent on its effects on vasculature, vascular control, and ventricular-vascular coupling. The clinical research on new agents has served to remind us how difficult it is to formulate the "ideal" positive inotropic or cardiovascular support drug for the critical care setting. The vast effort to develop a chronically and orally administrable drug to replace or even supplement digitalis has generally been disappointing. The dopaminergic agents (e.g., ibopamine, levodopa) act primarily via vasodilation and their effectiveness and role in managing heart failure remain unresolved. The initial excitement about the phosphodiesterase III inhibitors (e.g., amrinone, milrinone, enoximone) has been tempered by the results of large well-designed trials indicating variable effectiveness and a prominent adverse effect profile. During long-term oral administration none of these agents has been shown to improve clinical status or exercise capacity beyond that achieved by digoxin, when administered either separately or in combination with digoxin. The Prospective Randomized Milrinone Survival Evaluation (PROMISE) trial, showing that repeated oral administration of milrinone can increase mortality in heart failure, is having a devastating effect on the further development of this class of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Current status of non-digitalis positive inotropic drugs. 135 56

Using different subtypes of cyclic nucleotide phosphodiesterase (PDE) isoenzymes isolated from canine left ventricle, we identified R 80122, a 1,2,3,5-tetrahydro2-oxoimidazo[2,1-b]quinazoline derivative that was a more selective and potent inhibitor of PDE type III than milrinone or enoximone. Such substances improve cardiac contraction and relaxation, elicit vasodilation, and increase cardiac output (CO). To determine the extent to which these compounds affect the contractile force of stunned myocardium, the effects of enoximone, milrinone, and R 80122 on cardiac function were compared in anesthetized dogs subjected to 15-min occlusion of the left anterior descending coronary artery (LAD) followed by reperfusion, and treated beginning 30 min after reperfusion, with the compound being studied. During occlusion, all dogs exhibited passive systolic ventricular wall bulging in the ischemic area. Thirty minutes after reperfusion, systolic wall thickening was significantly decreased in the reperfused LAD segments and remained low (at 36% of baseline) in control animals. After enoximone administration, global left ventricular (LV) function was improved with i.v. doses greater than or equal to 0.64 mg/kg. Systolic wall thickening in the ischemic myocardium was restored less than or equal to 70% of baseline at 1.25 mg/kg i.v., but this dose also induced a marked decrease in arterial pressure and an increase in heart rate (HR). Milrinone and R 80122 significantly increased global LV function and systolic wall thickening in ischemic areas at doses greater than or equal to 0.16 mg/kg i.v. At the highest doses, HR increased slightly with both compounds.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparative effects of R 80122, enoximone, and milrinone on left ventricular phosphodiesterase isoenzymes in vitro and on contractility of normal and stunned myocardium in vivo in dogs. 138 69

The cardiac and hemodynamic effects of R80122, a new specific phosphodiesterase III inhibitor, were studied in a closed-chest canine model of acute global left ventricular ischemia complicated by heart failure. The results obtained were compared with those obtained with milrinone. Intravenous infusion of the compounds (0.005 mg/kg/min for both) was started when stable heart failure had developed and was continued for 50 min followed by a washout period of 60 min. Both R80122 and milrinone improved the function of the acutely failing heart, as indicated by the increase in the values of the variables related to left ventricular function, but differences existed. The most striking differences were the normalization of the left ventricular external mechanical efficiency with R80122, but not with milrinone, and the maintenance of aortic blood pressure during infusion of R80122, which decreased during infusion of milrinone. Milrinone tends to induce ventricular tachycardia more frequently than R80122. It can be concluded that R80122 and milrinone improve the function of the acutely failing heart, but that the changes induced by R80122 are better balanced, i.e., enhancement of external mechanical efficiency with maintenance of aortic blood pressure.
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PMID:Cardiac and hemodynamic effects of intravenous R80122, a new phosphodiesterase III inhibitor, in a canine model of myocardial ischemia and heart failure. 138 27

The effects of enoximone (MDL 17043, Perfan, CAS 77671-31-9) on the activities of the phosphodiesterase (PDE) isoenzymes I-IV and on force of contraction were investigated in ventricular preparations isolated from failing (end-stage myocardial failure, NYHA IV) and non-failing human hearts. In both tissues four PDE isoenzymes (PDE I-IV) with similar properties were separated by DEAE-sepharose chromatography. The effects of enoximone on PDE I-IV activities did not differ between non-failing and failing human hearts. As compared to PDE I (IC50 2100 mumol/l) and II (IC50 2900 mumol/l) enoximone is a selective PDE III (cGMP-inhibited PDE, IC50 5.9 mumol/l) and PDE IV (cGMP-insensitive PDE, IC50 21.1 mumol/l) inhibitor. Milrinone, 3-isobutyl-1-methylxanthine (IBMX) and UD-CG 212 Cl, a derivative of pimobendan, were studied in the failing heart for comparison. Milrinone inhibited PDE I-IV activities similar to enoximone, revealing IC50 values for inhibition of PDE III and IV (1.2 and 3.3 mumol/l) which were about two orders of magnitude lower than that of PDE I and II (173 and 306 mumol/l). UD-CG 212 Cl was the most potent (IC50 0.05 mumol/l) and most selective PDE III inhibitor tested (IC50 for PDE I, II and IV were 175, 181 and 40.8 mumol/l, resp.), whereas IBMX inhibited PDE I-IV nonselectively (IC50 15.3, 26.2, 5.6, 5.8 mumol/l, respectively). In trabeculae carneae from nonfailing and failing human hearts enoximone increased force of contraction only marginally by 18.0 +/- 9.1% (n = 8) and 24.5 +/- 8.7% (n = 9) of the predrug value.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phosphodiesterase inhibition by enoximone in preparations from nonfailing and failing human hearts. 138 15


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