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)

1 The effects of a newly developed dopamine-xanthine derivative, 7-propyl-theophylline-dopamine (D4975), have been examined in cats anaesthetized with sodium pentobarbitone. When administered intravenously (in doses as low as 0.5 to 1.0 micrograms/kg) it increased systemic arterial pressure, left ventricular (LV) dP/dtmax, dP/dt at fixed ventricular isovolumic pressures and cardiac output. Heart rate effects were minimal. 2 D4975 was about 5 times more active than dopamine or dobutamine in elevating LV dP/dtmax or dP/dt at common peak isovolumic pressures (CPIP) and about 10 times more active than dopamine at increasing systemic arterial blood pressure. The effects of D4975 were also more prolonged than those of the other two agents. 3 The effects of D4975 on LV dP/dtmax were greatly reduced by the prior administration of propranolol. D4975 has no effect on peripheral beta 2-adrenoceptors. 4 It is suggested that the effects of D4975 on the myocardium involve both beta 1-adrenoceptor stimulation and inhibition of phosphodiesterase and that the marked and prolonged pressor response is due to resistance to enzymatic breakdown by monoamine oxidase. 5 The results suggest that D4975 might prove valuable in the treatment of the hypotension and reduced myocardial contractility of shock, especially as it is possible to select a dose that increases LV dP/dtmax without increasing either heart rate of systemic arterial pressure.
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PMID:The cardiovascular pharmacology of 7-propyl-theo-phylline-dopamine (D4975); comparison with dopamine and dobutamine. 49 27

The present study investigated the effects of celiprolol a novel beta 1-antagonist with partial beta 2-agonist activity on the human failing heart. Experiments were performed on isolated electrically driven atrial and ventricular cardiac preparations and in membrane preparations from the left ventricles of nine patients (four with dilated cardiomyopathy; five with ischemic cardiomyopathy) undergoing cardiac transplantation for terminal heart failure. Celiprolol produced a negative inotropic effect in atrial and ventricular heart muscle. However, in the presence of forskolin--which activates the catalyst of the adenylate cyclase-or the cAMP phosphodiesterase inhibitor milrinone, celiprolol produced concentration-dependent positive inotropic effects and positive lusitropic effects. Experiments with the beta 1-and beta 2-selective antagonists CGP 207.12A and ICI 118.551, respectively, suggest that the positive inotropic response is mediated by beta 2-adrenoceptors. In radioligand binding experiments, a selectivity of 15.7 [-Gpp(NH)p] or 23.9 [+Gpp(NH)p] as judged from the Ki values--of binding to beta 2-adrenoceptors was measured in the failing human ventricular myocardium. Competition curves with celiprolol alone and in the presence of the guanine nucleotide Gpp(NH)p revealed no evidence for agonist activity at beta 1- or beta 2-adrenoceptors. It is concluded that amplification of the cAMP response is able to unmask partial agonist activity of celiprolol in the failing human heart at beta 2-adrenoceptors. The inotropic measurements are a more sensitive approach than radioligand binding studies. Whether the pharmacological profile of celiprolol will be useful in conditions like heart failure is questionable with respect to the potential downregulation of beta 2-adrenoceptors by its partial agonist activity.
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PMID:Positive inotropic effects due to partial agonistic activity of the beta-adrenoceptor antagonist celiprolol following amplification of cAMP formation in failing human myocardium. 127 96

Prenalterol, an allegedly beta 1-selective adrenergic agonist with high intrinsic sympathomimetic activity (ISA), was shown to be weakly lipolytic in rat adipocytes. However, in pertussis-toxin-treated adipocytes, the ISA of prenalterol was markedly increased (from 10-20% to approx. 100% of that of isoprenaline). The cellular sensitivity was also increased (EC50 approx. 60 nM and approx. 3 microM in pertussis-toxin-treated and control cells respectively). A similar effect was seen for other partial agonists such as the beta 2-selective agonist terbutaline and for beta-adrenergic antagonists with some intrinsic activity (metoprolol, pindolol). There was no clear change in sensitivity to isoprenaline's ability to stimulate adenylate cyclase in adipocyte membranes from pertussis-toxin-treated animals but the cyclase activity was increased approx. 4-fold in the presence of 1 microM-GTP. Prenalterol stimulated lipolysis by only small increases in intracellular cyclic AMP (cAMP) levels (less than 10% of that seen with isoprenaline). Basal lipolysis was increased in cells from pertussis-toxin-treated rats and the cellular sensitivity to the non-degradable cAMP analogue, N6-monobutyryl-cAMP, was increased. In control cells, a submaximal concentration of prenalterol (0.1 microM) increased the sensitivity to the cAMP analogues, N6-monobutyryl-cAMP and 8-bromo-cAMP. A low concentration (1 mM) of 8-bromo-cAMP also increased the effect of prenalterol. Similar effects were seen when the phosphodiesterase was inhibited. Thus (1) lipolysis is extremely sensitive to small increases in intracellular cAMP; (2) the degree of activation of adenylate cyclase and thus cAMP formation is the rate-limiting step for the biological response of partial agonists; (3) the inhibitory GTP-binding protein, Gi, is an important modulator ('tissue factor') of the beta-adrenergic agonistic property; (4) low levels of cAMP exert a priming effect on protein kinase A.
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PMID:The inhibitory GTP-binding protein (Gi) regulates the agonistic property of beta-adrenergic ligands in isolated rat adipocytes. Evidence for a priming effect of cyclic AMP. 128 Jan 15

In heart failure, the sympathetic nervous system is activated. The increased release of norepinephrine from the heart and the elevated levels of circulating catecholamines produce a downregulation of myocardial beta 1-adrenoceptors. In ischemic cardiomyopathy and mitral valve disease, a downregulation of beta 2-adrenoceptors has been observed also. The beta-adrenoceptor downregulation closely correlates to the reduced positive inotropic effects of beta-adrenoceptor agonists. In addition, an increase of the inhibitory guanine-nucleotide binding protein (Gi alpha) has been observed, while the levels of the stimulatory guanine-nucleotide binding protein (Gs alpha), the activity of the catalyst and the anti-adrenergic effects of A1-adenosine receptor- or m-cholinoceptor stimulation remain unchanged in the failing human heart. The increase of Gi alpha correlated closely to the reduced positive inotropic responses to the cAMP-phosphodiesterase inhibitor milrinone. In the failing human heart, the beta-adrenoceptor downregulation and the increased expression of Gi alpha represent pathobiochemical alterations which are involved in the reduced effects of cAMP-dependent positive inotropic agents. The therapeutic reversal of these pathobiochemical alterations is a future promise in the treatment of heart failure.
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PMID:[Adrenergic beta receptors and guanine nucleotide binding proteins (G-proteins) of the failing human heart]. 133 8

1. alpha 1-Adrenoceptor (phenylephrine in the presence of propranolol) and beta 2-adrenoceptor (fenoterol)-mediated positive inotropic effects were investigated in human ventricular preparations isolated from five non-failing (prospective organ donors) and from eight explanted failing hearts with end-stage idiopathic dilative cardiomyopathy (NYHA IV). 2. For comparison, the nonselective beta-adrenoceptor agonist isoprenaline, the phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX), the cardiac glycoside dihydroouabain, and calcium were studied. 3. Furthermore, the influence of IBMX on adenosine 3':5'-cyclic monophosphate (cyclic AMP) PDE activity as well as total beta-adrenoceptor density, beta 1- and beta 2-adrenoceptor subtype distribution, and alpha 1-adrenoceptor density were compared in nonfailing and failing human heart preparations. The radioligands (-)-[125I]-iodocyanopindolol for beta-adrenoceptor binding and [3H]-prazosin for alpha 1-adrenoceptor binding were used. 4. The inotropic responses to calcium and dihydroouabain in failing human hearts were unchanged, whereas the maximal alpha 1- and beta 2-adrenoceptor-mediated positive inotropic effects were greatly reduced. The inotropic effects of the other cyclic AMP increasing compounds, i.e. isoprenaline and IBMX, were also reduced to about 60% of the effects observed in nonfailing controls. The potency of these compounds was decreased by factors 4-10. 5. The basal PDE activity and the PDE inhibition by IBMX were similar in nonfailing and failing preparations. 6. The total beta-adrenoceptor density in nonfailing hearts was about 70 fmol mg-1 protein. In failing hearts the total number of beta-adrenoceptors was markedly reduced by about 60%. The betal/beta2-adrenoceptor ratio was shifted from about 80/20% in nonfailing to approximately 60/40% in failing hearts which was due to a selective reduction of beta1-adrenoceptors. The beta2-adrenoceptor population remaining unchanged. alpha-Adrenoceptor density was increased from about 4 fmol mg-' protein in nonfailing to 10 fmol mgprotein in failing hearts.7. Changes in PDE activity and adrenoceptor downregulation cannot completely explain the reduced positive inotropic effects of alpha 1- and beta 2-adrenoceptor agonists in failing human hearts. This supports the hypothesis that impairment of other processes such as the coupling between receptor and effector system, i.e. the respective G-proteins, are equally important in end-stage heart failure.
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PMID:Reduced alpha 1- and beta 2-adrenoceptor-mediated positive inotropic effects in human end-stage heart failure. 134 46

In the present study, we have tested the effects of transforming growth factor beta 1 (TGF beta 1) on FSH action toward aromatase activity and lactate production in cultured Sertoli cells isolated from immature porcine testes. Whereas treatment of Sertoli cells with FSH resulted in a dose-dependent increase (about 7-fold) in aromatase activity (conversion of testosterone into estradiol) (ED50 = 80 ng/ml FSH), the addition of TGF beta 1 reduced this gonadotropin action. The inhibitory effect of TGF beta 1 on FSH aromatase activity was dose dependent (ED50 = 0.1 ng/ml, 4 pM TGF beta 1) with a maximal decrease (about 40%) observed after a long term (48-h) treatment. TGF beta 1 exerted its inhibitory effect on FSH action at the level(s) of cAMP accumulation, exerting no apparent effect on the gonadotropin receptor or at a site(s) related to cAMP action. TGF beta 1 (2 ng/ml) significantly (P less than 0.002) reduced (52% decrease) FSH-stimulated cAMP levels in cultured porcine Sertoli cells. However, such an inhibitory effect of the growth factor was no longer observed when stimulation of cAMP accumulation with FSH occurred in the presence of methyl isobutyl xanthine (0.5 mM), an inhibitor of cAMP-phosphodiesterase activity. This observation suggests that TGF beta 1 decreased cAMP levels by increasing catabolism of the cyclic nucleotide through an enhancement of cAMP-phosphodiesterase activity. The inhibitory effect of TGF beta 1 was not limited to the action of FSH on aromatase activity but also extended to the gonadotropin action (mediated by cAMP) on lactate production. As for the inhibitory effect of TGF beta 1 on FSH-induced aromatase activity, the inhibitory effect of the growth factor on FSH-stimulated lactate production was dose and time dependent with a maximal decrease (about 30%) observed in the picomolar range (1 ng/ml, 40 pM) after 48 h treatment with TGF beta 1. In conclusion, the present study demonstrates that TGF beta 1 attenuates FSH action on Sertoli cell activity and that such inhibitory action is potentially exerted through a decrease in cAMP levels. Because of the local production of TGF beta 1, it is suggested that the effects of the growth factor reported here might be exerted in the context of the testicular paracrine mechanisms.
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PMID:Transforming growth factor beta 1 inhibits gonadotropin action in cultured porcine Sertoli cells. 137 Jul 96

Amrinone is the only phosphodiesterase fraction III inhibitor currently available in the USA for the treatment of perioperative biventricular failure. Patients with chronic congestive heart failure (CHF) show down-regulation of the beta 1-adrenergic receptor with a decrease in receptor density and altered responses to catecholamines. Intravenous administration of amrinone can transiently restore beta 1-adrenergic responses in patients who have CHF. Amrinone's mechanism of vasodilatation, independent of the beta 1-adrenergic receptor, nitrates, and calcium entry blockers, proves an important therapeutic option for pulmonary hypertension. The elimination half-life of amrinone in volunteers is 2.6-4.1 h, and 3.5 h when administered into the cardiopulmonary bypass (CPB) circuit. Different loading and infusion doses have been reported for amrinone. Investigators have demonstrated that increases in cardiac output following amrinone administration are directly related to plasma concentration. In cardiac surgical patients, following a dose of 0.75 mg kg-1 administered into the CPB circuit, plasma concentrations are subtherapeutic after 10 min. We believe that, when using amrinone to facilitate separation from CPB, a bolus dose of 1.5 mg kg-1 or more should be administered. If therapeutic levels need to be maintained in patients with biventricular failure, an infusion should also be administered after the bolus dose. Additive effects have been demonstrated when catecholamines are administered concomitantly with amrinone and other PDE III inhibitors to increase cyclic AMP in cardiac muscle and improve contractility. The use of amrinone with catecholamines is also important clinically, because together they attenuate the vasoconstrictive effects of catecholamines alone, while the catecholamines support perfusion pressure. Amrinone represents a novel drug for managing biventricular dysfunction in cardiac surgical patients.
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PMID:Perioperative experience with amrinone. 160 Sep 63

In patients with congestive heart failure, down-regulation of beta-adrenoceptors is present, probably as a result of sympathetic overstimulation. In end-stage dilated cardiomyopathy, beta 1-adrenoceptor density is markedly reduced, while beta 2-adrenoceptor density is normal. This latter finding does not necessarily imply normal sensitivity to beta 2-stimulation, due to possible alterations in the beta-adrenoceptor/adenylate cyclase complex beyond the receptor. In some disease states, such as ischemic cardiomyopathy and mitral valve disease, there seems to be a concomitant reduction of the beta 1- and beta 2-adrenoceptor density. The finding of beta-adrenoceptor down-regulation has stimulated the search for novel therapeutic approaches in heart failure patients. Beta-agonists could even further down-regulate beta receptors, and this perhaps explains why they seem not to be useful in long-term use. Agents that directly stimulate adenylate cyclase activity, such as forskolin, or that increase cyclic adenosine monophosphate degradation, such as the phosphodiesterase inhibitors, are being tested. Beta-adrenoceptor blocking agents were used in treatment of heart failure before beta-adrenoceptor down-regulation was recognized in these patients. It is tempting to speculate that the beneficial clinical and hemodynamic effects seen in these patients treated with metoprolol is indeed due to an antagonism of the beta-adrenoceptor down-regulation. Studies testing whether beta-adrenoceptor blocking agents can improve survival in congestive heart failure patients are on-going.
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PMID:Receptor function in heart failure. 164 66

During a 3-year period we administered enoximone, a phosphodiesterase inhibitor with positive inotropic and vasodilator properties, to 73 pretransplantation patients with end-stage heart failure who exhibited a clinical requirement for additional inotropic support. The clinical course and myocardial beta-adrenergic receptor status in the explanted hearts of these 73 patients was compared with results in 113 concurrently listed pretransplantation patients not requiring additional inotropic support. Only three patients required cessation of enoximone because of adverse effects, all from exacerbation of ventricular arrhythmias. Sixty-six of 73 (90.4%) enoximone-treated patients ultimately underwent cardiac transplantation a mean of 39.2 +/- 6.6 days (range 1 to 221 days) after starting enoximone, whereas seven patients (9.6%) died awaiting cardiac transplantation. The respective 1-, 3-, and 6-month pretransplantation survival rates of patients treated with enoximone calculated from their time on the waiting list for transplantation were 88.0%, 82.5%, and 82.5% compared with 92.1%, 83.8%, and 76.2% in control patients not receiving enoximone (all p = not significant). In 25 patients who received enoximone, ventricular myocardial beta-adrenergic receptors were measured at the time of transplantation and compared with values in failing ventricles from 52 pretransplantation patients not exposed to enoximone. Compared with ventricular myocardium of patients not given enoximone or intravenous beta-adrenergic agonists, total beta-adrenergic receptor (beta 1 plus beta 2) density was not decreased in patients treated with enoximone or enoximone plus intravenous beta-adrenergic agonists, but was decreased by 31% (p less than 0.05) in patients given intravenous beta-adrenergic agonists alone. Additionally, patients treated with enoximone had higher myocardial beta 2-adrenergic receptor densities than respective subgroups treated without (28% higher, p less than 0.01) or with (65% higher, p less than 0.01) intravenous beta-adrenergic agonists. Finally, isoproterenol- or calcium-mediated contractile responses in isolated right ventricular preparations from 14 patients treated with enoximone were similar to values in control patients not exposed to enoximone or intravenous beta-adrenergic agonists, suggesting that enoximone-related beta-adrenergic subsensitivity or damage to the contractile apparatus does not occur.
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PMID:Low-dose enoximone in subjects awaiting cardiac transplantation. Clinical results and effects on beta-adrenergic receptors. 165 Aug 67

Although recent studies indicate that MCI-154 exerts novel positive inotropic actions in heart muscle, the chronotropic properties of this new drug remain undefined. The present study compared the inotropic/chronotropic profile of MCI-154 with those of a nonselective beta 1/beta 2-agonist (isoproterenol, Iso) and a type III phosphodiesterase inhibitor (imazodan, CI-914) in cardiac preparations isolated from guinea pigs. The inotropic efficacy of MCI-154 was approximately equal to that of Iso and CI-194 in electrically paced (1 Hz) atrial muscle, with each agent increasing isometric contractile tension approximately 170% above basal (predrug) values. The inotropic EC50 for Iso (2.9 +/- 0.7 x 10(-9) M) was several orders of magnitude less than that for MCI-154 (1.4 +/- 0.4 x 10(-4) M) and CI-914 (1.1 +/- 0.2 x 10(-4) M). The inotropic potency of MCI-154 was equivalent in atrial and left ventricular myocardium. Both Iso and CI-194 substantially increased spontaneous beating frequency of sinoatrial preparations, and the inotropic/chronotropic potency ratio for each was unity. In contrast, MCI-154 exerted a slight negative chronotropic action on basal sinoatrial rate. Moreover, the negative chronotropic influence of MCI-154 was increased several-fold in the presence of Iso-stimulated maximal increases in heart rate (HR), and this inhibitory chronotropic action of MCI-154 was not prevented by muscarinic receptor blockade with atropine. These findings indicate that MCI-154 has a unique inotropic/chronotropic profile in cardiac tissues of guinea pigs in that this drug (a) efficaciously increased myocardial contractility, (b) had minimal effect on basal sinoatrial automaticity and yet (c) markedly inhibited sympathetically mediated sinus tachycardia.
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PMID:Inotropic and chronotropic profile of MCI-154: comparison with isoproterenol and imazodan in guinea pig cardiac preparations. 169 67


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