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:3.5.4.4 (adenosine deaminase)
5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Platelets have been shown to protect isolated perfused rat hearts from injury and dysfunction after ischemia and reperfusion. We examined the role of platelet-derived adenosine in the cardioprotective effects of platelets against reperfusion injury. Isolated perfused rat hearts were subjected to 40-min global ischemia followed by 30-min reperfusion. The buffer-perfused hearts developed dysfunction, as indicated by 40 +/- 4% decrease in force of cardiac contraction (FCC) and 24 +/- 3% increase in coronary perfusion pressure (CPP). Creatine kinase (CK) was released in coronary effluent during reperfusion, indicating myocardial injury. At the end of reperfusion, myocardial CK content and superoxide dismutase (SOD) activity were lower than in sham ischemia-reperfused hearts. Perfusion of hearts with washed platelets resulted in protection against myocardial dysfunction and injury after ischemia and reperfusion, indicated by preservation of FCC (-2 +/- 5%) and CPP (-3 +/- 2%) (both p < 0.01 vs. buffer-perfused hearts). Myocardial CK and SOD activity were also preserved, and release of CK in the coronary effluent was minimal (all p < 0.05 vs. buffer-perfused hearts). The cardioprotective effects of platelets were attenuated by preincubation of platelets with adenosine deaminase. Perfusion with adenosine or the adenosine2 receptor agonist N6-[2-(3,5-dimethoxyphenyl)-2-(2- methylphenyl)-ethyl]adenosine (DPMA) also protected heart from myocardial dysfunction and injury after ischemia and reperfusion. Both adenosine and DPMA had salutary effects on indexes of cardiac injury. Platelet-derived adenosine contributes at least in part to the cardioprotective effects of platelets against ischemia and reperfusion in isolated rat heart.
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PMID:Platelet-derived adenosine contributes to the cardioprotective effects of platelets against ischemia-reperfusion injury in isolated rat heart. 753 56

Short-term hibernating myocardium is characterized by reduced contractile function during persistent ischemia, the recovery of metabolism over time, a recruitable inotropic reserve, and the lack of necrosis. The mechanisms underlying myocardial hibernation are unclear. The present study addressed the role of endogenous adenosine and that of activation of ATP-dependent potassium (KATP) channels. In 22 enflurane-anesthetized swine, coronary inflow was reduced to decrease regional myocardial work (W, measured by sonomicrometry) by 60-70% at 5 min of ischemia; this flow reduction has previously been shown to be compatible with the development of myocardial hibernation. Systemic hemodynamics, W, subendocardial blood flow (measured by microspheres), and the myocardial creatine phosphate content (measured by biopsies, mumol/g wet wt) were measured under control conditions and during 90 min of ischemia, with an intracoronary dobutamine infusion during the last 5 min of ischemia. The impact of endogenous adenosine was eliminated by infusion of intracoronary adenosine deaminase (ADA), and the impact of activation of KATP channels by glibenclamide. Creatine phosphate content recovered in the placebo-treated swine (n = 8, 3.8 +/- 1.9 to 5.8 +/- 2.0 mumol/g wet wt) as well as in swine receiving ADA (n = 7, 4.1 +/- 1.2 to 6.0 +/- 1.7 mumol/g wet wt) or glibenclamide (n = 7, 2.8 +/- 1.3 to 6.7 +/- 1.6 mumol/g wet wt) when ischemia was prolonged from 5 to 85 min. At the end of 90 min of ischemia, W increased during intracoronary dobutamine in all three groups to a comparable extent, and myocardial necrosis was absent in all three groups of swine.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regional short-term myocardial hibernation in swine does not involve endogenous adenosine or KATP channels. 761 80

This study was designed to determine whether intermittent warm aortic crossclamping induces cumulative myocardial stunning or if the myocardium becomes preconditioned after the first episode of ischemia in canine models in vivo. The role of adenosine triphosphate catabolism and subsequent release of purines on reperfusion-mediated postischemic ventricular dysfunction and arrhythmias was assessed with the use of selective inhibitors of nucleoside transport, p-nitrobenzylthioinosine (NBMPR), and a specific adenosine deaminase inhibitor, erythro-9-[2-hydroxy-3-nonyl] adenine (EHNA). Thirty-two anesthetized dogs were instrumented to monitor left ventricular contractility, off bypass, by sonomicrometry. During cardiopulmonary bypass dogs were treated before ischemia with either saline solution (control group, n = 8) or EHNA (100 mumol/L) and NBMPR (25 mumol/L) (EHNA/NBMPR group, n = 8). Hearts were subjected to either 60 minutes of global ischemia and 120 minutes of reperfusion (n = 16) or 6 episodes of 10 minutes of global ischemia and 10 minutes of reperfusion, followed by 60 minutes of reperfusion (n = 16). Sixty minutes of sustained ischemia resulted in 80% loss of adenosine triphosphate and induced reperfusion-mediated ventricular fibrillation and severe left ventricular dysfunction in the control group. EHNA/NBMPR treatment augmented myocardial adenosine trapping during ischemia, attenuated ventricular fibrillation, and enhanced left ventricular functional recovery, despite similar depletion of adenosine triphosphate (80% loss). In the intermittent ischemia experiment, the first episode of 10 minutes of ischemia and reperfusion caused significant adenosine triphosphate depletion, ventricular fibrillation, and left ventricular stunning in both control and drug-treated groups. The prevalence of ventricular fibrillation was greater in the control group than in the drug-treated group after the first episode of ischemia (p < 0.05). Adenosine was the major nucleoside accumulated in the myocardium at the end of 10 minutes of ischemia in the EHNA/NBMPR-treated group (p < 0.05 versus control). Subsequent episodes of ischemia prevented ventricular fibrillation and did not cause cumulative left ventricular stunning in either group. Left ventricular function fully recovered in the EHNA/NBMPR-treated group after intermittent ischemia, but remained stunned in the control group. Unlike sustained ischemia, intermittent ischemia and reperfusion preserved myocardial adenosine triphosphate, limited purine release, and prevented ventricular fibrillation and cumulative stunning. These results suggest that intermittent ischemia and reperfusion augmented the endogenous protective mechanism or mechanisms of "preconditioning." Nucleoside trapping improved functional recovery after sustained or repetitive ischemia. It is concluded that adenosine triphosphate preservation or blockade of nucleoside transport may play an important role in the activation of endogenous myocardial protective mechanisms that "precondition" against subsequent ischemic stress.
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PMID:Intermittent aortic crossclamping prevents cumulative adenosine triphosphate depletion, ventricular fibrillation, and dysfunction (stunning): is it preconditioning? 869 80

Pentostatin (2-deoxycoformycin) is a potent inhibitor of adenosine deaminase and has been demonstrated to augment endogenous adenosine levels during regional and global myocardial ischemia. Based on the rationale that increasing endogenous adenosine during ischemia may be cardioprotective, the objective of this study was to determine if adenosine deaminase inhibition with pentostatin could improve postischemic contractile dysfunction (stunning) in open-chest anesthetized dogs. All animals underwent 15 min of coronary occlusion followed by 3 h of reperfusion preceded by an intravenous bolus of either 0.2 mg/kg of pentostatin (n = 8) or saline (n = 7). Sonomicrometers were placed in the ischemic area and were used to measure systolic wall thickening before, during, and after occlusion of the left anterior descending artery. Myocardial blood flow was measured with tracer labeled microspheres at baseline, 10 min of occlusion and at 1 h of reperfusion. Both groups were equally dyskinetic during occlusion (-21 +/- 5% of baseline thickening in the controls and -28 +/- 8% in the pentostatin group). The pentostatin group, however, demonstrated better contractile function at all time points during reperfusion, which was significantly different from the control group at 3 h of reperfusion. The improvement in regional function in the pentostatin group was not due to significant disparities in hemodynamic variables, size of the region at risk, or in collateral blood flow. These results indicate that pentostatin can ameliorate the severity of myocardial stunning, an effect we propose is due to increasing endogenous levels of adenosine during the ischemic interval. Although significant improvement was detected with pentostatin, the improvement was modest compared to controls, suggesting that the utility of inhibiting adenosine deaminase to modify regional mechanical stunning is limited.
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PMID:Effect of adenosine deaminase inhibition with pentostatin on myocardial stunning in dogs. 764 20

Because adenine nucleotide catabolites may be important during postischemic lung reperfusion, we examined the pathway of adenosine monophosphate (AMP) degradation in ischemic lung tissue. Once the pattern of degradation is known, pharmacological interventions can be considered, offering new methods of reducing lung reperfusion injury. For this purpose we used the isolated rabbit lung. Rabbit lungs were flushed in situ with a modified Krebs Henseleit solution (60 ml/kg). The lungs were removed and stored deflated, immersed in saline solution at 37 degrees C. At regular times, biopsies were taken, and adenine nucleotides, nucleosides, and bases were measured in these biopsies using high performance liquid chromatography (HPLC). During lung ischemia, a very significant increase of inosine monophosphate (IMP) was found. Adenosine levels on the other hand did not increase. Hypoxanthine was the major end catabolite of ischemic lung tissue (constituting 92% of the nucleoside and purine base fraction at 4 hours ischemia). To further determine the pathway of AMP degradation, 400 mM of the adenosine deaminase inhibitor erythro-9-[2-hydroxy-3-nonyl]adenine (EHNA) was added to the lung flush solution. During ischemia, adenosine triphosphate (ATP) breakdown was unaltered but adenosine became the major catabolite (2.8 times the concentration of hypoxanthine at 4 hours ischemia). These data suggest that: 1) in rabbit lung tissue, dephosphorylation of AMP to adenosine is more important than deamination to IMP; 2) hypoxanthine is the major end catabolite of ischemic lung tissue. By inhibiting the enzyme deaminase, reduced hypoxanthine levels and increased adenosine levels were obtained. Pharmacological interventions are now available to interfere with the formation of adenine nucleosides and bases in ischemic lung tissue. The importance of adenine nucleotide catabolites to postischemic lung reperfusion injury is discussed.
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PMID:Pattern of AMP degradation in ischemic rabbit lung tissue. 773 34

A new method for the rapid determination of plasma adenosine concentrations was developed by using high-performance liquid chromatography with a column switching technique and fluorometric detection. Several "stop solutions" were used to prevent the enzymatic degradation and cellular uptake and release of adenosine in blood samples. Red blood cells and certain denatured proteins were separated by centrifugation. Subsequently, the supernatant was transferred directly into autosample vials and adenosine was reacted with chloroacetaldehyde to form a strong fluorescent, 1-N6-ethenoadenosine. The adenosine derivative was injected directly and separated on a shielded hydrophobic phase column coupled with a C18 reverse-phase column using a column switching valve. Macromolecules and other interfering substances were excluded by the shielded hydrophobic phase column and bypassed to waste. Then, the adenosine derivative and other retained compounds were switched onto the reverse-phase column for further separation and subsequently to the fluorescence detector. The system reduces the analysis time and contamination of the column and hence allows a shorter cleanup time and a longer column lifetime. Adenosine as low as 30 fmol (signal-to-noise ratio, S/N = 3) can be detected by this method. The percentage of recovery of adenosine in plasma treated with adenosine deaminase was above 90%. This method is very rapid (without tedious sample preparation) and sensitive for determining adenosine in canine blood and should prove to be useful in analyzing the effects of ischemia and reperfusion on arterial and coronary venous adenosine concentrations in blood or perfusate samples released from the ischemic or hypoxic myocardium.
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PMID:Determination of plasma adenosine by high-performance liquid chromatography with column switching and fluorometric detection. 788 74

This study tests the hypothesis that the adenosine deaminase inhibitor pentostatin (2-deoxycoformycin), when given before ischemia or during infusions of blood cardioplegia, augments interstitial adenosine levels and prevents postcardioplegia dysfunction in hearts with antecedent ischemia. Twenty-one anesthetized dogs were placed on cardiopulmonary bypass, and the hearts were made globally ischemic for 30 minutes. Dogs received blood cardioplegia with no pentostatin (BCP group, n = 6), pretreatment pentostatin (0.2 mg/kg) infused 5 minutes before global ischemia (PS-PTx group, n = 7), or pentostatin included only in the blood cardioplegia without pretreatment (PS-BCP group, n = 8). Microdialysate myocardial adenosine levels (an index of interstitial fluid levels) increased only modestly in the BCP group (from 0.55 +/- 0.13 microM to 2.64 +/- 0.50 microM) and the PS-BCP group (from 0.55 +/- 0.18 microM to 1.08 +/- 0.48 microM) during normothermic ischemia, but interstitial adenosine levels were not augmented further during cardioplegic arrest in either group. In contrast, the adenosine level in the PS-PTx group was significantly (p < 0.05) augmented during global ischemia (from 0.50 +/- 0.13 microM to 63.16 +/- 28.08 microM) and cardioplegia infusion (to 15.26 microM +/- 5.61 microM). Relative to baseline, postischemic left ventricular performance (end-systolic pressure-volume relation) was depressed in both the BCP (from 5.5 +/- 1.2 mm Hg/mL to 3.8 +/- 0.4 mm Hg/mL) and PS-BCP groups (from 7.1 +/- 0.9 mm Hg/mL to 3.8 +/- 0.7 mm Hg/mL). In contrast, PS-PTx restored postischemic performance (from 6.2 +/- 0.5 mm Hg/mL to 7.5 +/- 0.9 mm Hg/mL).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pentostatin-augmented interstitial adenosine prevents postcardioplegia injury in damaged hearts. 794 94

An experimental comparative study on isolated guinea pig lungs has been undertaken to determine the probable beneficial effects of adding selenium to pulmonary preservation solutions in lung ischemia. The isolated lungs (n = 10 in each group) previously being perfused by oxygenated Krebs-Henseleit solution were put in normothermic ischemic conditions just after the infusion of 30 ml of pulmonary preservation solution (Euro-Collins in the control group, Euro-Collins plus selenium 10(-3) mol in the experiment group). After 3 hours of normothermic ischemia the lungs were reperfused with the same buffer for 20 minutes. Pulmonary artery pressures, tissue malondialdehyde levels, and adenosine deaminase levels of the perfusate were measured before and after the ischemic period and also at the end of reperfusion. An electron microscopic analysis was performed on the lung tissues at the end of the experimental procedure. According to our data, the addition of selenium to pulmonary preservation solution showed a significant protective effect regarding both ischemic and reperfusion injury.
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PMID:The role of selenium added to pulmonary preservation solutions in isolated guinea pig lungs. 796 76

We sought to determine the role of adenosine in the sustained but reversible decrease in cardiac neurotransmission that occurs after brief ischemia. Adult mongrel dogs were anesthetized and instrumented for measurements of heart rate, arterial pressure, and left anterior descending coronary artery (LAD) and left circumflex coronary artery (LCX) flow velocities. Changes in coronary vascular resistance were measured during bilateral stimulation of the stellate ganglia. After beta-adrenergic blockade and bilateral vagotomy, stellate stimulation increased coronary vascular resistance in the LAD and LCX beds 28 +/- 2% and 30 +/- 3%, respectively. After a 15-minute infusion of adenosine into the LAD, the peak increase in LAD resistance was significantly reduced (18 +/- 2%) compared with LCX (34 +/- 5%) and control (P < .05, n = 6) resistance. The LAD response after infusion of the vasodilator papaverine was unchanged (n = 6). Intracoronary infusion of adenosine deaminase (n = 10) but not vehicle (n = 5) into the LAD during a 15-minute LAD occlusion prevented the attenuation in constriction to stellate stimulation. We conclude that adenosine, exogenously infused or endogenously produced, is capable of reducing cardiac neurotransmission.
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PMID:Role of adenosine in postischemic dysfunction of coronary innervation. 800 Dec 82

A previous study has shown that endogenous adenosine trapping during ischemia (by blocking adenine nucleoside transport and inhibiting adenosine breakdown) prevents myocardial stunning. In this study, we tested the hypothesis that delay of administration of inhibitors until reperfusion would similarly prevent myocardial stunning in the absence of entrapped adenosine. In both studies, a selective nucleoside transport blocker, p-nitrobenzyl-thioinosine, was used in combination with a potent adenosine deaminase inhibitor, erythro-9-(2-hydroxy-3-nonyl)adenine, to entrap adenosine (preischemic treatment) or inosine (postischemic treatment) in an in vivo canine model of reversible global ischemia. Twenty-five anesthetized adult dogs were instrumented (by sonomicrometry) to monitor left ventricular performance from the relationship between stroke work and end-diastolic length as a sensitive and load-independent index of contractility. Hearts of animals supported by cardiopulmonary bypass were subjected to 30 minutes of normothermic global ischemia and 60 minutes of reperfusion. Saline solution containing the pharmacologic agents were infused into the bypass circuit before ischemia (group 1) or during reperfusion (group 2). Control group (group 3) received saline before and after ischemia. Myocardial biopsy specimens were obtained before, during, and after ischemia, and levels of adenine nucleotides, nucleosides, oxypurines, and the oxidized form of nicotinamide-adenine dinucleotide were determined. Left ventricular contractility fully recovered within 30 minutes of reperfusion in the groups treated with erythro-9-(2-hydroxy-3-nonyl)adenine and p-nitrobenzyl-thioinosine (p < 0.05 versus control group). Myocardial adenosine triphosphate was depleted by 50% in all groups at the end of ischemia. Adenosine triphosphate recovered during reperfusion only in the group that was treated with inhibitors before ischemia (group 1). At the end of ischemia, adenosine levels were low (< 10% of total nucleosides) in the control group (group 3) and in the group treated only after ischemia (group 2). A high level of adenosine (> 90% of total nucleosides) was present in group 1. We infer that selective pharmacologic blockade of nucleoside transport, only after ischemic injury, accelerated functional recovery during reperfusion, even without trapping of endogenous adenosine during ischemia and without adenosine triphosphate recovery during reperfusion. Recovery of myocardial adenosine triphosphate required preischemic treatment and adenosine entrapment during ischemia and reperfusion. Therefore, nucleoside trapping may be used to prevent reperfusion-mediated injury after reversible ischemic injury.
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PMID:Nucleoside trapping during reperfusion prevents ventricular dysfunction, "stunning," in absence of adenosine. Possible separation between ischemic and reperfusion injury. 804 Nov 75


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