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)

APP 201-533 [3-amino-6-methyl-5-phenyl-2(1H)-pyridinone] was investigated in vivo in anesthetized and unanesthetized dogs and pithed open-chest cats and in vitro in guinea pig atria and papillary muscles, skinned muscle fibers from pig hearts, and rat myocardium. Left ventricular dP/dt was increased in anesthetized dogs after intravenous injection of 0.2 and 2 mg/kg APP 201-533 (34 +/- 3 and 132 +/- 28%, respectively) and in unanesthetized dogs after oral doses of 1.5-7.5 mg/kg (34 +/- 11-138 +/- 43%). The substance induced moderate tachycardia. Large intraduodenal doses of APP 201-533 reduced afterload in anesthetized dogs. The compound does not seem to act either by stimulation of alpha- or beta-adrenoceptors or histamine receptors or by liberation of catecholamines. APP 201-533 up to 10(-5) M had no electrophysiological effect on normal action potentials in guinea pig papillary muscles. A phosphodiesterase-inhibiting activity (IC50 = 1.6 X 10(-4) M) may be responsible for the positive inotropic action. Another key to the mechanism of action may be based on our observation of a shift of the relationship between cardiac force and intracellular Ca2+ concentration. In contrast to amrinone and ouabain, APP 201-533 increases Ca2+ sensitivity of the myocardial contractile structures.
J Cardiovasc Pharmacol
PMID:Pharmacological actions of APP 201-533, a novel cardiotonic agent. 241 Jun 94

The possible mechanism of action of the positive inotropic agent APP 201-533 [3-amino-6-methyl-5-phenyl-2(1H)-pyridinone] was investigated. In guinea pig papillary muscles, APP 201-533 increased force of contraction concentration dependently at 10(-4)-10(-3) M. The effect was associated with an abbreviation of contraction and relaxation time. In guinea pig papillary muscles partially depolarized with 22 mM K+, APP 201-533 in concentrations of 10(-4) and 10(-5) M restored slow action potentials, which were not influenced by cimetidine, propranolol, and prazosin but were blocked by the Ca2+ antagonist PY 108-068 and by carbachol in an atropine-sensitive manner. The concentration-effect curve of histamine was shifted to the left in the presence of APP 201-533. These actions can be explained by the increase in cardiac cyclic AMP level that was found in rabbit papillary muscles and guinea pig left atria treated with APP 201-533 due to the known phosphodiesterase inhibitory effect of pyridinones. APP 201-533 increased the inotropic potency of dihydroouabain in guinea pig papillary muscles. It seems possible that this effect is based on an increased Ca2+ sensitivity of myocardial contractile structures as described previously for APP 201-533.
J Cardiovasc Pharmacol
PMID:Positive inotropic and electrophysiological effects of APP 201-533 can be explained by an increase of cardiac cyclic AMP. 241 Jun 95

The mechanism of the inotropic effect of piroximone HCl [MDL 19205A, 4-ethyl-1,3-dihydro-5-(4-pyridinylcarbonyl)-2H-imidozol-2-on e HCl] was studied in the cat papillary muscle paced electrically in vitro. Piroximone produced a concentration-dependent positive inotropic effect accompanied by an increase in rate of contraction and rate of relaxation, but abbreviated time to peak tension and relaxation time. The positive inotropic effect produced by piroximone was antagonized by carbachol, 3 X 10(-6) M, whereas that produced by increasing calcium concentration was not affected by carbachol. In potassium chloride (22 mM) depolarized muscle, piroximone restored contractility, which was not affected by propranolol (10(-6) M) or by tetrodotoxin (2 X 10(-5) M), but was inhibited by nifedipine (10(-7) M). Piroximine also elevated tissue cyclic AMP (cAMP) content in the papillary muscle. Although nifedipine inhibited the restoration of contractility, it did so without altering the increase of cAMP produced by piroximone. These results suggest that piroximone causes an increase in calcium influx that is mediated by an increase in cAMP, and the results are consistent with the hypothesis that specific inhibition of the high affinity cAMP phosphodiesterase (PDE III) plays a role in the positive inotropic effect of piroximone.
J Cardiovasc Pharmacol
PMID:Studies on the mechanism of the positive inotropic effect of piroximone in cat papillary muscle. 241 Jul 17

The pharmacological nature of purinoceptors in the rabbit coronary artery was investigated by comparing the extent of vasorelaxation induced by various purine derivatives, with or without amino group at C6 and with or without ribose at N9 in the purine structure. These derivatives were grouped according to structure--adenosine, inosine, adenine, and hypoxanthine analogs. The vasorelaxations produced by adenosine analogs were inhibited by aminophylline, while relaxations produced by the other three groups were unaffected. In the case of adenosine analogs, modification of amino group at C6 to secondary amine resulted in reduction of the potency of the vasorelaxing effect. The order of potency was as follows: adenosine greater than N6-(L)-phenylisopropyladenosine greater than N6-(D)-phenylisopropyladenosine greater than N6-cyclohexyl-adenosine greater than N6-(2,5-dioxo-3-pyrrolidinyl)-adenosine greater than kinetine riboside greater than N6-methyladenosine. On the other hand, the aminophylline-resistant relaxations of adenine analogs were augmented by modification of amino group at C6 to secondary or to tertiary amine. The order of potency was as follows: 6-cyclohexylaminopurine greater than 6-dimethylaminopurine greater than kinetine greater than 6-methylaminopurine adenine. Of adenosine, N6-cyclohexyladenosine, adenine, C6-cyclohexylaminopurine, and inosine, N6-cyclohexylaminopurine was the most potent phosphodiesterase inhibitor of crude enzyme prepared from rabbit aorta. From the order of potency of relaxations produced by adenosine analogs, adenosine receptors in the rabbit coronary artery seem to be of the A2-subtype. The relaxation induced by aminophylline-resistant adenine analogs may be due to activation of an unknown but specific site, since there is a structure-activity relationship in the relaxations produced by this group. Such relaxations may be linked to inhibition of phosphodiesterase in the rabbit coronary artery.
J Cardiovasc Pharmacol
PMID:Relaxations of isolated rabbit coronary artery by purine derivatives: A2-adenosine receptors. 242 75

This study was undertaken to characterize the cardiac electrophysiological and mechanical effects of MDL 19205, a new and potent nonglycoside, positive inotropic agent. In addition, intracellular Na+ activity (aiNa) was measured to determine if this agent might produce its inotropic effects by increasing aiNa and secondarily by increasing intracellular calcium via Na+ -Ca2+ exchange. Experiments were conducted in free-running trabecular muscles and Purkinje fibers obtained from sheep hearts. The following were the most significant effects of MDL 19205: a decrease in action potential duration in both ventricular and Purkinje tissues; a cumulative dose-dependent increase in contractile force in ventricular muscle but not in Purkinje strands; no change in aiNa in Purkinje fibers to accompany the positive inotropic effect of this agent; a shift in the dose-response relation by approximately fourfold in the presence of beta-adrenergic blockade with sotalol (10(-7) M); an enhancement of diastolic depolarization in Purkinje fibers resulting in automaticity that is accelerated by overdrive; and a potentiation of the positive inotropic effects of MDL 19205 by 8-bromo-cAMP (1 mM), indicating a potent phosphodiesterase inhibitory action of MDL 19205. These results suggest that MDL 19205 exerts at least part of its positive inotropic and automatic actions through stimulation of beta-adrenergic receptors. This action occurs in conjunction with its ability to inhibit phosphodiesterase, thus promoting an accumulation of cAMP in cardiac cells. Other intracellular actions may also contribute to the effect of this drug, but they do not rely on an increase in aiNa or dramatic changes in the action potential plateau or duration.
J Cardiovasc Pharmacol
PMID:Effects of MDL 19205 (piroximone), a new cardiotonic agent, on electrophysiological, mechanical, and intracellular ionic characteristics of sheep cardiac tissues. 242 79

Milrinone is a new inotropic agent for the treatment of refractory congestive heart failure. Our understanding of the mechanisms(s) of action of this synthetic cardiotonic drug is incomplete. We examined the effects of milrinone and the parent compound amrinone on sarcoplasmic reticulum function (45Ca-uptake and Ca-ATPase); radioligand binding to adenosine, beta-adrenergic, and cholinergic muscarinic receptors; cyclic AMP accumulation; and inhibition of various forms of cyclic AMP phosphodiesterases. Comparisons were made to observe how these effects correlate with the inotropic response of heart. Milrinone was shown to be a potent phosphodiesterase inhibitor that was 40 times more potent than amrinone and 10 times more potent at inhibiting the high-affinity (Km = 0.23 microM) form (Ki = 22 microM) than the low-affinity (Km = 140 microM) form (Ki = 225 microM) of cyclic AMP phosphodiesterase in heart. The potency of milrinone as a phosphodiesterase inhibitor was the same in the presence and absence of calcium. Concentrations of milrinone that increased cyclic AMP accumulation also produced positive inotropy. A comparison of milrinone with amrinone and methylxanthines revealed the order of potency to be isobutylmethylxanthine greater than milrinone greater than theophylline greater than caffeine greater than amrinone. Milrinone and amrinone had no effect on 45Ca-uptake or Ca-ATPase activity in myocyte sarcoplasmic reticulum. However, milrinone did bind weakly to adenosine receptors (KD = 466 microM) but not to cholinergic muscarinic or beta-adrenergic receptors. Also, in combination with isoproterenol high concentrations of milrinone blocked the negative inotropic response to the adenosine agonist phenylisopropyladenosine.(ABSTRACT TRUNCATED AT 250 WORDS)
J Cardiovasc Pharmacol
PMID:Biochemical mechanisms for the inotropic effect of the cardiotonic drug milrinone. 242 30

The adenylate-cyclase activator forskolin, the guanylate-cyclase stimulator sodium nitroprusside, the phosphodiesterase inhibitor Ro 15-2041, different Ca-entry blockers, as well as various vasodilators, and the atrial natriuretic peptide were tested for antiplatelet activity. Thrombin, vasopressin, ADP, arachidonic acid, and the dihydropyridine Ca agonist CGP 28392 were used as platelet activators. The physiological and biochemical parameters of platelet function studied included shape-change reaction, intracellular free-Ca modulation, and cyclic nucleotide formation. When inhibition of the shape-change response occurred, it was accompanied by inhibition of the increase in intracellular free Ca. Furthermore, the results suggest a possible intracellular site of action of Ca entry blockers in platelets, and confirm the importance of modulation of cyclic nucleotides in the regulation of platelet function, regardless of the mechanism of platelet activation. Additional antiplatelet activity of antihypertensive agents may have a beneficial effect in reducing the associated risk of thrombo-embolic complications in essential hypertension.
J Cardiovasc Pharmacol 1986
PMID:Vasodilating agents and platelet function: intracellular free calcium concentration, cyclic nucleotides, and shape-change response. 243 9

We investigated the mechanisms of the direct positive inotropic effect (PIE) of helenalin, a sesquiterpene lactone isolated from the plant genus Helenium of the family Compositae in guinea pig ventricular myocardium. Helenalin (3 X 10(-4) M) produced biphasic PIEs (first and second PIE phases) on normal nonreserpinized papillary muscles, driven at 1 Hz in Krebs-Henseleit solution at 30 degrees C. The first PIE phase was abolished by reserpine treatment. Helenalin increased the force of "rested-state contraction" in a manner similar to that of other cyclic AMP-elevating substances, such as norepinephrine and IBMX (3-isobutyl-1-methylxanthine). In isometric contraction curves of the papillary muscle stimulated at 0.2 Hz, helenalin showed two clear peaks of an early and a late component. Carbachol preferentially suppressed the late component of contraction, a component that is clearly apparent in the presence of intracellular cyclic AMP-increasing substances. Helenalin potentiated the PIEs of isoproterenol and histamine but not that of dihydroouabain. In the presence of a phosphodiesterase (PDE) inhibitor (IBMX 10(-3) M), helenalin did not produce any PIE. In electrophysiological studies, helenalin prolonged the duration of transmembrane action potentials of papillary muscle. In partially depolarized muscles (external K+ = 30 mM), helenalin increased the overshoot and the duration of the slow action potential. These results led to the conclusion that helenalin produces an elevation of cyclic AMP through PDE inhibition, thereby increasing Ca2+ influx which enhances the contractility of the myocardium by increasing Ca2+ release from the SR.
J Cardiovasc Pharmacol 1987 Feb
PMID:Mode of cardiotonic action of helenalin, a sesquiterpene lactone, on guinea pig ventricular myocardium. 243 98

The actions of SK&F 94120, a selective phosphodiesterase (PDE III) inhibitor, have been characterised on human ventricular myocardium obtained from heart failure patients. Some actions have been compared directly with those of the drug on guinea pig and cat ventricular myocardium. SK&F 94120 caused positive inotropic responses in preparations from all three species. In the human preparations, there was no evidence of differential activity in ventricles obtained from patients with heart failure associated with ischaemic heart disease, congestive cardiomyopathy, or mitral valve disease. The mechanism of positive inotropic activity of SK&F 94120 demonstrated characteristics of PDE III inhibition--e.g., potentiation of isoprenaline responses and reversal by carbachol. In addition, in human tissue a highly significant correlation between positive inotropic activity and increases in intracellular cAMP was demonstrated. Electrophysiological studies in human and guinea pig myocardium demonstrated that SK&F 94120 enhanced the second inward Ca2+ current over the same concentration range as that needed for positive inotropic activity. This was demonstrated in preparations incubated in Krebs bicarbonate solution and, more clearly, in solutions with raised K+ concentration. The data described in this report establish that inhibition of PDE III is an effective positive inotropic mechanism in human ventricular myocardium. Comparison of the responses in human, guinea pig, and cat myocardium shows clear similarities of responses with only small quantitative differences.
J Cardiovasc Pharmacol 1987 Jun
PMID:Analysis of responses to a selective phosphodiesterase III inhibitor, SK&F 94120, on isolated myocardium, including human ventricular myocardium from "end-stage" failure patients. 244 40

Prolonged isoproterenol infusion (400 micrograms/kg/h for 4 days) in rats was previously shown to produce a reduction in the sensitivity of both cardiac and vascular beta-adrenergic receptors without affecting responsiveness to alpha 1 agonists or phosphodiesterase inhibitors in either vascular or cardiac muscle. The present study was designed to determine if the loss in beta receptor responsiveness was similar for both beta 1 and beta 2 vascular receptors. The rat jugular vein was previously shown to relax in response to both norepinephrine and isoproterenol with norepinephrine-induced relaxation being mediated by interaction with beta 1 adrenergic receptors and isoproterenol-induced relaxation being mediated by its interaction with beta 2 vascular receptors. Using this preparation, tissues from isoproterenol-infused rats were approximately threefold less responsive to isoproterenol when compared to responses in tissues from saline-treated rats. Relaxation to norepinephrine in jugular veins from isoproterenol-infused rats was virtually abolished relative to the response in saline-treated animals. These data suggest that beta 1-adrenergic receptors in blood vessels are considerably more susceptible to down regulation than are beta 2-adrenergic receptors. This observation may have importance in both the therapy of congestive heart failure, where down regulation of beta-adrenergic receptors has been observed, and in our understanding of the mechanism for the inotropic effects of beta receptor agonists.
J Cardiovasc Pharmacol 1987 Sep
PMID:Selective down regulation of vascular beta 1 adrenergic receptors after prolonged isoproterenol infusion. 244 87


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