Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Effects of regional ischemia on myocardial glycolysis were studied by measuring the levels of glycolytic intermediates in the endo- and epicardial layers of the left ventricle in dogs anesthetized with pentobarbital. Regional ischemia was induced by ligating a small branch of the left anterior descending coronary artery. The myocardial tissue samples were removed before and 1.5, 3, 7, or 30 min after coronary artery ligation. Based on a crossover plot study of the glycolytic intermediates, it is suggested that the activity of glycogen phosphorylase was accelerated, while that of phosphofructokinase was inhibited in ischemic myocardium samples removed 1.5, 3, 7, and 30 min after ligation. When the frozen myocardium was allowed to stand at room temperature for 10 min, the crossover plot study revealed acceleration of phosphofructokinase activity. The metabolic response to regional ischemia of the endocardial layers was more marked than that of the epicardial. During ischemia the levels of adenine nucleotides did not change significantly, but those of citrate and hydrogen ions increased significantly. It appears that inhibition of myocardial phosphofructokinase activity during ischemia is partly due to an increase in the levels of citrate and hydrogen ions in the ischemic tissue.
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PMID:Crossover plot study of glycolytic intermediates in the ischemic canine heart. 621 59

Under conditions of acute ischemia spontaneous fibrillation which developed in heart ventricles as well as arrhythmias which were medicamentally provoked both were accompanied by a decrease in activity of glycogen phosphorylase a. At the same time, there was a distinct increase of non-phosphorylated isoenzyme ratio to the total phosphorylase activity of the tissue and the total glycogen pool was decreased. The decrease in activity of glycogen phosphorylase a, after pharmacological correction of metabolism of highly ischemized myocardium using obzidan and digoxin at therapeutic doses, occurred simultaneously with a decrease in the level of phosphorylase b activity in the tissue. A hypothesis, considering an increase in glycogenolysis as a trigger mechanism in development of ventricle fibrillation under conditions of acute coronary occlusion, is criticized.
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PMID:[Role of glycogenolysis inhibition in the etiology of arrhythmias in coronary disease]. 715 22

The effect of silymarin on liver cell damage induced by ischemia was studied in rats fasted for 24 h. In the first series of experiments in vitro ischemia was induced by storing tissue blocks in closed vials at 37 degrees C for 15, 30, 45 and 60 min. Cell injury was detected by the cytophotometrical measurement of glycogen phosphorylase activity in unfixed cryostat sections demonstrated by a modified histochemical procedure. In the second series of experiments in vivo ischemia was provoked by clamping the afferent vessels to the median and left lateral lobes of the liver for 60 min, followed by removal of the clamp and reperfusion. The extent of cell damage was determined by measuring the ALAT and ASAT activities in serum at 1, 3, 6 and 24 h after ischemia and by quantifying the extent of necrosis in the liver after 24 h reperfusion by measuring the unstained areas in cryostat sections incubated for lactate dehydrogenase activity. Silymarin (100 mg/kg b.w.) was administered intravenously at 5 min before both the induction of ischemia and the restoration of blood flow (in vivo ischemia) and at 1 h and at 5 min before sacrifice (in vitro ischemia). Controls received an equal amount of saline. The serum amino-transferase activities after 24 h reperfusion were significantly reduced in the silymarin-treated group (n = 10); ALAT 293 +/- 193 U/L, ASAT 343 +/- 229 U/L compared with the control group (n = 7): ALAT 1238 +/- 743 U/L, ASAT 948 +/- 541 U/L (p < 0.03), and the extent of necrosis decreased from 25.6 +/- 16.0% ( n = 7) to 7.8 +/- 8.3% (n = 10) (p < 0.01) after treatment with silymarin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Protective effect of silymarin on rat liver injury induced by ischemia. 828 22

In the present study we have investigated whether enzyme histochemical parameters can be applied to detect early ischemic damage in rat heart after ischemia without restoration of the blood flow. Ischemia was induced by incubating heart fragments for 0, 10, 20, 30, 60, 120 and 240 min at 37 degrees C. The activity and localization of the following enzymes was studied in unfixed cryostat sections using quantitative histochemical methods: lactate dehydrogenase, creatine kinase, succinate dehydrogenase, phosphofructokinase, acid phosphatase, 5'-nucleotidase and glycogen phosphorylase. Moreover, the ultrastructure of the tissue was studied with special attention to the appearance of flocculent densities in mitochondria, which can be seen as a sign of irreversible cell damage. It was shown that glycogen phosphorylase activity in rat heart decreased after short periods (30 min) of in vitro ischemia, whereas all other enzymes studied were not decreased up to 240 min, with the exception of lactate dehydrogenase and phosphofructokinase activities which were diminished only at 240 and 120 min of ischemia, respectively. Some reaction product was found after incubating for 5'-nucleotidase activity in the absence of substrate, indicating the presence of endogenous substrate(s). This endogenous substrate disappeared from the myocytes after 20 min of ischemia. It is assumed that AMP and/or other phosphate-containing compounds play an essential role in the activation of glycogen phosphorylase. Significant reduction of glycogen phosphorylase activity is correlated with the irreversible stage of damage of myocytes as judged from the ultrastructure.
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PMID:Histochemical detection of glycogen phosphorylase activity as parameter for early ischemic damage in rat heart. 850 31

Prior transient episodes of ischemia ("ischemic preconditioning") reduce lactate accumulation and attenuate acidosis during a subsequent prolonged ischemic insult. The mechanisms responsible for attenuated glycolytic catabolite accumulation have not been established but may include earlier exhaustion of glycogen stores, slowed glycogenolysis before complete glycogen depletion, and/or inhibition of glycolysis. Simultaneous repeated measures of myocardial glycogen and the rates of glycolysis, glycogenolysis, glucose utilization, and glycolytic ATP production were obtained during total ischemia by 13C nuclear magnetic resonance spectroscopy in control and ischemia-preconditioned isolated rat hearts. Both [13C]glycolytic and [13C]glycogenolytic rates were significantly lower during total ischemia in preconditioned compared with control hearts (0.77 +/- 0.04 versus 1.06 +/- 0.06 mumol/min per gram wet weight [P < .01] for glycolysis and 0.15 +/- 0.07 versus 0.78 +/- 0.12 mumol/ min per gram wet weight [P < .001] for glycogenolysis, respectively, at 2.5 minutes of ischemia). Slowed glycolysis was present even during the early minutes of ischemia, when significant amounts of available [13C]glycogen were still present. Importantly, the reduction in the rate of glycogenolysis was larger and out of proportion to the reduction in glycolysis and occurred despite an increase in glucose utilization in preconditioned hearts (2.23 +/- 0.15 versus 1.5 +/- 0.10 mumol/min per gram wet weight at 1.25 minutes, P < .01). During early ischemia, conversion of glycogen phosphorylase to the a or "active" form was less in preconditioned than in control hearts (29.1 +/- 2.6% versus 41.2 +/- 9.8%, respectively; P < .05). Taken together, these findings demonstrate that ischemic preconditioning significantly depresses glycolytic catabolite accumulation during sustained ischemia not by more severe glycolytic inhibition or exhaustion of glycogen stores but by depressed glycogenolysis from the onset of ischemia.
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PMID:Attenuated glycogenolysis reduces glycolytic catabolite accumulation during ischemia in preconditioned rat hearts. 878 77

This review deals with glycogen phosphorylase (GP) and its isoenzyme BB in the diagnosis of ischaemic myocardial injury. Early identification and confirmation of acute myocardial infarction is essential for correct patient care and disposition decision in the emergency department. In this respect, glycogen phosphorylase isoenzyme BB (GPBB) based on its metabolic function is an enzyme for early laboratory detection of ischaemia. In the aerobic heart muscle GPBB together with glycogen is tightly associated with the vesicles of the sarcoplasmic reticulum. Release of GPBB, the main isoform in the human myocardium, essentially depends on the degradation of glycogen, which is catalyzed by GP. Ischaemia is known to favour the conversion of bound GP in the b form into GP a, thereby accelerating glycogen breakdown, which is the ultimate prerequisite for getting GP into a soluble form being able to move freely in the cytosol. The efflux of GPBB into the extracellular fluid follows if ischaemia-induced structural alterations in the cell membrane become manifest. The clinical application of GPBB as a marker of ischaemic myocardial injury is a very promising tool for extending our knowledge of the severity of myocardial ischaemic events in the various coronary syndromes. The rational roots of this development were originated from Albert Wollenberger's research work on the biochemistry of cardiac ischaemia and the transient acceleration of glycogenolysis mainly brought about by GP activation.
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PMID:Glycogen phosphorylase isoenzyme BB in diagnosis of myocardial ischaemic injury and infarction. 890 85

The role played by glycogenolysis in the ischemic heart has been recently put into question because it is suspected that a slowing down of this process could be beneficial for the tolerance of the myocardium to ischemia. The role of the intracellular effectors that control the rate of glycogenolysis has therefore regained interest. We aimed to understand the role played by those intracellular effectors which are directly related to the energy balance of the heart. To this end, we review some of the previously published data on this subject and we present new data obtained from P-31 and C-13 NMR spectroscopic measurement on isolated rat heart. Two conditions of ischemia were studied: 15 min global no-flow and 25 min low-flow ischemia. The hearts were isolated either from control animals or from rats pre-treated with isoproterenol (5 mg.kg-1 b.w. i.p.) 1 h before the perfusion in order to C-13 label glycogen stores. Our main results are as follows: (1) the biochemically determined glycogenolysis rate during the early phase of ischemia (up to 10-15 min) was larger in no-flow ischemia than in low-flow conditions for both groups, (2) direct measurement of the glycogenolysis rate, as determined by C-13 NMR, after labelling of the glycogen pool in the hearts from isoproterenol-treated rats, confirms the estimations from the biochemical data, (3) glycogenolysis was slower in the hearts from pre-treated animals than in control hearts for both conditions of ischemia, (4) the total activity of glycogen phosphorylase (a + b) increased, by 50%, after 5 min no-flow ischemia, whereas it decreased by 42% after the same time of low-flow ischemia. However, the ratio phosphorylase a/a + b was not altered, whatever the conditions, (5) the concentration of inorganic phosphate (Pi) increased sharply during the first minutes of ischemia, to values above 8-10 mM, under all conditions studied. The rate of increase was larger during no-flow ischemia than during low-flow ischemia. The concentration of Pi was thereafter higher in controls than in the hearts from isoproterenol-treated animals. The calculated cytosolic concentration of free 5'AMP increased sharply at the onset on ischemia, reaching in a few minutes values above 30 microM in controls and significantly lower values around 15 microM, in the hearts from isoproterenol-treated rats. (6) The hearts from isoproterenol-treated rats displayed a reduced intracellular acidosis, when compared to controls, under both conditions of ischemia. We conclude that the intracellular effectors, mainly free AMP, play an essential role in the control of glycogenolysis via allosteric control of phosphorylase b activity. The alteration in the concentration of free Pi, the substrate of both forms of phosphorylase, can be considered as determinant in the control of the rate of glycogenolysis. The attenuation of ischemia-induced intracellular acidosis in the hearts from isoproterenol-treated rats could be a consequence of a reduced glycogenolytic rate and is likely to be related to a better resumption of the mechanical function on reperfusion.
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PMID:Crucial role of intracellular effectors on glycogenolysis in the isolated rat heart: potential consequences on the myocardial tolerance to ischemia. 890 83

The acute coronary syndromes represent a continuum of myocardial ischemia ranging from angina, reversible tissue injury --> unstable angina, frequently associated with minor myocardial damage --> myocardial infarction and extensive tissue necrosis. Historically, coronary artery disease assessment has been mainly binary, using WHO criteria of symptoms, electrocardiography, and biochemical markers. The creatine kinase-MB isoenzyme (CK-MB) has been a benchmark for markers, but it is not specific for myocardium. Cardiac-specific isoforms of troponin T and I have emerged as sensitive myocardial infarction (MI) indicators and, importantly, for risk stratification of acute coronary syndrome patients. In addition to markers of myocardial cell necrosis, markers of plaque disruption (C-reactive protein and serum amyloid A), "angry" platelets (P-selectin), ischemia (glycogen phosphorylase-BB isoenzyme), and the procoagulant state and thrombosis (soluble fibrin) have potential use. Also, CK-MB and myoglobin have been combined with clinical indicators for monitoring reperfusion after thrombolytic therapy. Biochemical markers will continue to be an important clinical adjunct for MI diagnosis, risk assessment, and reperfusion monitoring in the future.
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PMID:Biochemical markers of the acute coronary syndromes. 970 95

Metabolism, monitored via in situ catalytic enzyme histochemistry and fine structure, was studied in the myocardium of chronic diabetic male Wistar rats administered L-arginine (12.8 mg/100 g/day) for 24 weeks. Diabetes was induced with a single i.v. injection of 55 mg/kg streptozotocin. After 6 months, the tissue of the left ventricle was processed for electron microscope examination and transmural tissue blocks were frozen for enzyme histochemistry. In diabetic myocardium, heterogeneous ischemia-like subcellular alterations of cardiomyocytes and capillaries were observed, together with interstitial fibrosis. This structural remodeling was accompanied by significantly decreased activity of endothelial nitric oxide synthase (NOS) and heterogeneously decreased activities of glycogen phosphorylase (GlPh), hydroxybutyrate dehydrogenase (HBDH) and adenosine triphophatases (ATPases) throughout the myocardium. In arginine-treated diabetic rats, there was evidence of protected structural integrity of endothelial cells and attenuated structural disturbances of cardiomyocytes. This was associated with the markedly preserved histochemical activities of all detected enzymes in comparison with nontreated diabetic rats (NOS 98.7 +/- 10.5% vs. 35.4 +/- 4.1%; ATPases 82.7 +/- 9.1% vs. 69.3 +/- 5.2%; GlPh 65.2 +/- 8.3% vs. 45.5 +/- 3.8%; HBDH 68.9 +/- 8.5% vs. 44.1 +/- 6.7% of control values). The results indicate that long-term supplementation of L-arginine may account for the reduction of diabetes-induced myocardial structural remodeling.
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PMID:L-arginine reduces structural remodeling in the diabetic rat myocardium. 1209 6

Ischemia-modified albumin is the first biomarker for myocardial ischemia to be approved by the FDA. Other markers are being evaluated such as free fatty acids, pregnancy-associated plasma protein-A, glycogen phosphorylase isoenzyme BB, sphingosine-1-phosphate and whole blood choline. This area of clinical research will continue to grow, given the importance of detecting myocardial ischemia. Which marker or combination of markers will, ultimately, be the best approach awaits further research.
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PMID:The ischemia-modified albumin biomarker for myocardial ischemia. 1284 Oct 70


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