EC:2.7.11.13 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Functional studies were performed on human peripheral blood T lymphocytes stained with goat anti-5'-nucleotidase antibodies and separated into ecto-5'-nucleotidase (ecto-5'-NT)-positive and -negative populations using the FACSTAR fluorescence-activated cell sorter. On the average, ecto-5'-NT+ T cells contained 34 +/- 13% CD4+ and 55 +/- 15% CD8+ cells, whereas ecto-5'-NT-T cells contained 65 +/- 12% CD4+ and 23 +/- 8% CD8+ cells. Staining with anti-5'-NT antibodies did not significantly alter the ability of unseparated T cells to proliferate in response to PHA or PMA, or in a MLR. However, prior incubation with anti-5'-NT antibodies did inhibit the ability of irradiated T cells to provide help for PWM-stimulated Ig synthesis by as much as 55%. In five separate experiments, ecto-5'-NT-T cells demonstrated an equal or better ability to incorporate [3H]TdR after PHA stimulation or in a MLR, as compared with ecto-5'-NT+ T cells. Similarly, ecto-5'-NT- T cells were not diminished in their ability to provide help for autologous B cells in a PWM-driven system. Clearly, the inability of ecto-5'-NT- T cells from patients with a variety of immunodeficiency diseases to function in these assays cannot be explained solely by their lack of ecto-5'-NT activity. In contrast, ecto-5'-NT-positive and -negative T cells showed markedly different dose-response curves for proliferation in response to PMA. Ecto-5'-NT+ T cells responded to lower doses of PMA (1.0 ng/ml) than did ecto-5'-NT- T cells and showed a two- to eight-fold greater rate of [3H]TdR incorporation at 3 to 10 ng of PMA per ml. Ecto-5'-NT+ T cells may have a protein kinase C that is more accessible or more easily activated or may utilize an alternate pathway of activation when stimulated with low concentrations of PMA.
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PMID:Functional characterization of ecto-5'-nucleotidase-positive and -negative human T lymphocytes. 253 56

Both ischemia and hypoxia increase adenosine production in the heart. This study tested whether hypoxia increases adenosine production in the coronary artery via ecto-5'-nucleotidase and the role of protein kinase C in this condition. Canine left circumflex coronary artery was rapidly removed and incubated in 10 mL Krebs-Henseleit solution for 30 minutes. The Krebs-Henseleit solution contained 5'-iodotubercidin and 2'-deoxycoformycin, which inhibit adenosine kinase and adenosine deaminase, respectively. Adenosine production was measured in intact coronary arteries under normoxic conditions (16.2 +/- 1.2 pmol/mg protein). Adenosine production was reduced by 27% after removal of endothelium. Ecto-5'-nucleotidase activity of coronary arteries with and without endothelium was 51 +/- 6 and 41 +/- 4 nmol/mg protein per minute under normoxic conditions. Hypoxia increased adenosine production to 27.0 +/- 2.3 and 20.0 +/- 0.8 pmol/mg protein with and without endothelium. Hypoxia also increased ecto-5'-nucleotidase activity of coronary arteries with and without endothelium (74 +/- 8 and 53 +/- 5 nmol/mg protein per minute; P < .05). Increases in adenosine production under hypoxic conditions were blunted by both an inhibitor of ecto-5'-nucleotidase and inhibitors of protein kinase C. Activation of ecto-5'-nucleotidase was blunted by an inhibitor of protein kinase C. These results indicate that hypoxia increased extracellular adenosine production and activated ecto-5'-nucleotidase via activation of protein kinase C in coronary arterial smooth muscle and endothelial cells. Increased adenosine production in coronary arteries during hypoxia may contribute to coronary vasodilation and cardioprotection against ischemic injury.
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PMID:Activation of protein kinase C increases adenosine production in the hypoxic canine coronary artery through the extracellular pathway. 748 56

Adenosine, synthesized by ecto-5'-nucleotidase, is cardioprotective against ischemia and reperfusion injury. We have previously reported that activation of protein kinase C increases ecto-5'-nucleotidase activity of the rat cardiomyocytes, raising the possibility that activation of protein kinase C protects cardiomyocytes from the irreversible cellular injury via activation of ecto-5'-nucleotidase. To test this hypothesis, cardiomyocytes were isolated from adult male Wistar rats and suspended in modified HEPES-Tyrode buffer solution. The cardiomyocytes were incubated with and without exposure to methoxamine (1 x 10(-6) mol/l) or phorbol 12-myristate 13-acetate (PMA. 1 x 10(-8) mol/l). Ecto-5'-nucleotidase activity increased 15 min after the onset of an exposure to either methoxamine or PMA. Adenosine release during hypoxia and reperfusion was augmented in the methoxamine- and PMA-pretreated cardiomyocytes compared with the untreated cardiomyocytes, which was inhibited by alpha, beta-methyleneadenosine 5'-diphosphate (AOPCP), an inhibitor of ecto-5'-nucleotidase. Irreversible cellular injury assessed by the extent of release of lactate dehydrogenase and the trypan blue exclusion test following 60 min of hypoxia and 60 min of reoxygenation was attenuated in the methoxamine- and PMA-pretreated cardiomyocytes compared with the untreated group, which was also blunted by AOPCP and 8-sulfophenyltheophylline, an adenosine receptor antagonist. An adenosine A1 receptor agonist, N6-cyclohexyladenosine, restored the cardioprotection under the treatment with PMA and AOPCP. We conclude that activation of ecto-5'-nucleotidase via protein kinase C contributes to the attenuation of the irreversible injury of the rat cardiomyocytes due to hypoxia and reoxygenation.
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PMID:Activation of ecto-5'-nucleotidase by protein kinase C attenuates irreversible cellular injury due to hypoxia and reoxygenation in rat cardiomyocytes. 889 53

1. Ischaemic preconditioning (IP) protects the myocardium against irreversible ischaemic injury by activating protein kinase C (PKC). The mechanism by which PKC protects the myocardium is unknown. We have shown that PKC increases the activity of ecto-5'-nucleotidase (ecto-5'-N) and thereby the production of adenosine in cardiomyocytes which may protect the myocardium against ischaemia-reperfusion injury in vivo. 2. The objective of this study was to elucidate the possible role of PKC-induced activation of ecto-5'-N in the cardioprotection associated with IP in the canine heart. 3. IP increased the activities of both ecto-5'-N and PKC, and minimized ischaemic damage (infarct size: 7.5 +/- 1.8 vs. 42.3 +/- 2.8%, P < 0.01 vs. the control group). Treatment with the PKC activator (4 beta-phorbol 12-myristate-13-acetate) also reduced infarct size (13.5 +/- 2.9%, P < 0.01 vs. the control group). 8-Sulfophenyltheophylline (an antagonist of adenosine receptors) or alpha,beta-methyleneadenosine 5'-diphosphate (an inhibitor of ecto-5'-N) eliminated the cardioprotective effect of the PKC activator (infarct size: 36.6 +/- 3.9 and 34.7 +/- 4.2%, respectively), suggesting that PMA limits infarct size by increasing the activity of ecto-5'-N and the adenosine level. 4. The PMA-induced cardioprotection was blunted by GF109203X (an inhibitor of PKC, infarct size: 36.2 +/- 3.1%), but not by pretreatment with dexamethasone (infarct size, 14.2 +/- 2.6%). 5. We conclude that the PMA- and IP-induced cardioprotection is attributable to phosphorylation and activation of ecto-5'-N.
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PMID:Activation of ecto-5'-nucleotidase by protein kinase C and its role in ischaemic tolerance in the canine heart. 911 20

1. To determine whether protein kinase C (PKC)-mediated activation of ecto-5'-nucleotidase would increase interstitial adenosine concentrations in the rat heart in vivo, we made use of the microdialysis technique and a flexibly mounted probe, which was implanted in the left ventricular myocardium and perfused with Tyrode solution. 2. The baseline level of dialysate adenosine was 0.51 +/- 0.09 microM (n = 16). Perfusion of adenosine 5'-monophosphate (AMP, 100 microM) through the probe increased the dialysate adenosine concentration markedly to 9.25 +/- 0.46 microM (n = 15). alpha, beta-Methyleneadenosine 5'-diphosphate (AOPCP, 100 microM), an inhibitor of ecto-5'-nucleotidase, abolished the AMP-induced increase in dialysate adenosine, but did not affect the baseline level of adenosine. These observations suggest that the dialysate adenosine obtained during the perfusion with AMP, but not the baseline levels of adenosine, originated from the dephosphorylation of AMP by ecto-5'-nucleotidase. Thus, the level of adenosine measured during AMP perfusion gives an index of the activity of ecto-5'-nucleotidase in the tissue. 3. Noradrenaline (10 microM) increased the adenosine concentration measured in the presence of 100 microM AMP (i.e. the activity of ecto-5'-nucleotidase) by 38.7 +/- 9.6% (n = 5, P < 0.05), an increase which was inhibited by an antagonist of the alpha 1-adrenoceptor (prazosin, 50 microM) or of PKC (chelerythrine, 10 microM). Further application of either the alpha 1-adrenoceptor agonist methoxamine (100 microM) or the diacylglycerol analogue 1,2-dioctanoyl-sn-glycerol (DOG, 100 microM) also increased the adenosine concentration by 35.1 +/- 10.0% (n = 6, P < 0.05) or 40.6 +/- 8.3% (n = 5, P < 0.05), respectively. 4. The presence of okadaic acid (50 microM), an inhibitor of protein phosphatase, enhanced the noradrenaline-induced increase in adenosine concentration by 112.4 +/- 35.9% (n = 4, P < 0.05), to a level significantly (P < 0.05) greater than the increase caused by noradrenaline alone (38.7 +/- 9.6%). 5. These data provide the first evidence that alpha 1-adrenoceptor stimulation and the subsequent activation of PKC can increase adenosine concentrations in interstitial spaces of ventricular muscle in vivo, through activation of endogenous ecto-5'-nucleotidase.
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PMID:Stimulation of alpha 1-adrenoceptors and protein kinase C-mediated activation of ecto-5'-nucleotidase in rat hearts in vivo. 928 80

We have reported that activation of protein kinase C (PKC) increases ecto-5'-nucleotidase activity, which may contribute to the infarct size-limiting effect of ischemic preconditioning. Since we have reported that Ca(2+)- and phospholipid-sensitive PKC is activated due to ischemic preconditioning, we further tested 1) whether PKC-alpha or -beta is translocated to the cellular membrane of the preconditioned canine myocardium, and 2) whether activation of PKC contributes to the increase in ecto-5'-nucleotidase activity via phosphorylation-dependent mechanisms. Four times of 5 minutes coronary occlusion separated by 5 minutes of reperfusion (ischemic preconditioning) translocated PKC-alpha to the cellular membrane in the canine hearts, although PKC-beta, -delta, -epsilon, and -zeta were not translocated. The activity of Ca(2+)- and phospholipid-sensitive PKC increased, which was attenuated by the removal of either Ca2+ or phosphatidylserine. Ecto-5'-nucleotidase was also activated in the preconditioned myocardium compared with control. Inhibition of PKC due to GF109203X blunted the activation of myocardial ecto-5'-nucleotidase. Okadaic acid (an inhibitor of phosphatase) enhanced the increases in ecto-5'-nucleotidase activity due to preconditioning, and this enhancement was blunted by GF109203X. We conclude that ischemic preconditioning activates PKC-alpha, and thus ecto-5'-nucleotidase.
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PMID:Role of protein kinase C-alpha in activation of ecto-5'-nucleotidase in the preconditioned canine myocardium. 934 90

1. Adenosine plays a crucial role in the evolution of ischemic preconditioning. With the use of microdialysis techniques in in situ rat hearts, we assessed the activity of ecto-5'-nucleotidase (a key enzyme responsible for adenosine production), and examined the effects of lysophosphatidylcholine (LPC) on the production of interstitial adenosine. 2. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rat hearts and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP, 100 microM). With this system, the dialysate adenosine originates from the dephosphorylation of AMP, catalyzed by endogenous ecto-5'-nucleotidase. The level of dialysate adenosine is a measure of the ecto-5'-nucleotidase activity in vivo. 3. LPC at concentrations of 25 and 50 microM significantly increased the level of dialysate adenosine to 122.7+/-4.3% (n=4, P<0.05) and 158.6+/-7.2% (n=5, P<0.05) of the control, respectively. Chelerythrine (200 microM), a protein kinase C (PKC) inhibitor, completely abolished the increase of dialysate adenosine afforded by LPC (50 microM) (n=5). 4. These data provide the first evidence that LPC does increase the concentration of interstitial adenosine in rat hearts in situ, through the PKC-mediated activation of endogenous ecto-5'-nucleotidase.
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PMID:Effects of lysophosphatidylcholine on the production of interstitial adenosine via protein kinase C-mediated activation of ecto-5'-nucleotidase. 980 32

We examined the effect of tyramine on the production of adenosine in rat heart. A flexibly mounted microdialysis setup was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5'-nucleotidase in in vivo rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP) at a rate of 1.0 microl/min. The concentration of adenosine in the effluent (dialysate) was measured by high-performance liquid chromatography (HPLC). Dialysate adenosine obtained during perfusion with the AMP-containing solution through the probe originated from the hydrolysis of AMP by endogenous ecto-5'-nucleotidase, and the level of adenosine reflected the activity of ecto-5'-nucleotidase in the tissue. Tyramine (0-4 mM) increased the adenosine concentration measured during the perfusion of AMP (100 microM) in a concentration-dependent manner. Alpha,beta-methyleneadenosine 5'-diphosphate (alpha,beta-meADP, 100 microM), an inhibitor of ecto-5'-nucleotidase, abolished the AMP-induced increase in dialysate adenosine. Tyramine (1 mM) increased the adenosine concentration measured in the presence of 100 microM AMP (i.e., the activity of ecto-5'-nucleotidase) by 65.8 +/- 19.9% (n = 6, P < 0.05), an increase which was inhibited by an antagonist of the alpha1-adrenoceptor (prazosin, 50 microM) or of protein kinase C (chelerythrine, 10 microM). These data provide the first evidence that alpha1-adrenoceptor stimulation and the subsequent activation of protein kinase C can increase adenosine concentrations in the interstitial space of ventricular muscle in vivo, through activation of endogenous ecto-5'-nucleotidase. To examine the effect of tyramine on the production of adenosine by ischemia-reperfusion of the rat myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery. When the heart was reperfused, elevation of the level of adenosine in the ischemic zone was observed, but this change was not significant. However, when corresponding experiments were performed with a subsequent systemic administration of tyramine (1 mM), a marked elevation in the level of adenosine was observed. The results suggest that tyramine elevates adenosine via stimulation of alpha1-adrenoceptors and protein kinase C-mediated activation of ecto-5'-nucleotidase in rat heart.
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PMID:Tyramine produces interstitial adenosine-mediated activation of ecto-5'-nucleotidase in rat heart in vivo. 1042 37

Biological and mechanical stressors such as ischemia, hypoxia, cellular ATP depletion, Ca2+ overload, free radicals, pressure and volume overload, catecholamines, cytokines, and renin-angiotensin may independently cause reversible and/or irreversible cardiac dysfunction. As a defense against these forms of stress, several endogenous self-protective mechanisms are exerted to avoid cellular injury. Adenosine, a degradative substance of ATP, may act as an endogenous cardioprotective substance in pathophysiological conditions of the heart, such as myocardial ischemia and chronic heart failure. For example, when brief periods of myocardial ischemia precede sustained ischemia, infarct size is markedly limited, a phenomenon known as ischemic preconditioning. We found that ischemic preconditioning activates the enzyme responsible for adenosine release, ie, ecto-5'-nucleotidase. Furthermore, the inhibitor of ecto-5'-nucleotidase reduced the infarct size-limiting effect of ischemic preconditioning, which establishes the cause-effect relationship between activation of ecto-5'-nucleotidase and the infarct size-limiting effect. We also found that protein kinase C is responsible for the activation of ecto-5'-nucleotidase. Protein kinase C phosphorylated the serine and threonine residues of ecto-5'-nucleotidase. Therefore, we suggest that adenosine produced via ecto-5'-nucleotidase gives cardioprotection against ischemia and reperfusion injury. Also, we found that plasma adenosine levels are increased in patients with chronic heart failure. Ecto-5'-nucleotidase activity increased in the blood and the myocardium in patients with chronic heart failure, which may explain the increases in adenosine levels in the plasma and the myocardium. In addition, we found that further elevation of plasma adenosine levels due to either dipyridamole or dilazep reduces the severity of chronic heart failure. Thus, we suggest that endogenous adenosine is also beneficial in chronic heart failure. We propose potential mechanisms for cardioprotection attributable to adenosine in pathophysiological states in heart diseases. The establishment of adenosine therapy may be useful for the treatment of either ischemic heart diseases or chronic heart failure.
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PMID:Adenosine and cardioprotection in the diseased heart. 1047 69

We examined whether reserpine-induced norepinephrine (NE) depletion attenuated the products of adenosine in rat heart. A flexibly mounted microdialysis technique was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5'-nucleotidase in rat hearts in situ. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP) at rate of 1.0 microliter/min. The baseline level of dialysate adenosine was 0.51 +/- 0.09 microM. The introduction of AMP (100 microM) through the probe increased markedly the dialysate adenosine to 8.95 +/- 0.86 microM, and this increase was inhibited by ecto-5'-nucleotidase inhibitor, alpha, beta-methyleneadenosine 5'-diphosphate (AOPCP, 100 microM), to 0.66 +/- 0.38 microM. Thus, the level of dialysate adenosine is a measure of the ecto-5'-nucleotidase activity in the tissue in situ. AMP concentration for the half-maximal effect of adenosine release (EC(50)) was 107.3 microM. The maximum attainable concentration of dialysate adenosine (E(max)) by AMP was 21.1 microM. However, the EC(50) and E(max) values with reserpinized animals were 106.9 and 7.1 microM, respectively. Electrical stimulation of the left stellate ganglion increased significantly dialysate adenosine concentration, from the control level of 8.66 +/- 0.96 microM to 12.38 +/- 1.11 microM. After stimulation, dialysate adenosine returned to near the prestimulation level. When corresponding experiments were performed with reserpinized animals, the effect of electrical stimulation was abolished. Tyramine (endogenous catecholamine trigger) increased the adenosine concentration in a concentration-dependent manner. However, the elevation of adenosine concentration with reserpinized animals was not observed. These results suggest that reserpine attenuates NE-induced adenosine via stimulation of alpha(1)-adrenoceptor and protein kinase C mediated activation of ecto-5'-nucleotidase in rat heart.
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PMID:Reserpine attenuates interstitial adenosine-mediated activation of ecto-5'-nucleotidase in rat hearts in vivo. 1070 Mar 89

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