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)

The effect of diltiazem (d-cis-diltiazem) on the ischemic myocardium was compared with that of l-cis-diltiazem, an optical isomer having less potent calcium channel-blocking action, in the isolated, perfused working rat heart. Ischemia decreased mechanical function and tissue levels of ATP and creatine phosphate, and increased tissue levels of nonesterified fatty acids (NEFA), AMP and lactate. Reperfusion did not restore mechanical function, but restored incompletely the levels of metabolites (except NEFA) that had been altered by ischemia. The ischemia-induced changes in NEFA were prevented by d-cis-diltiazem completely and by l-cis-diltiazem incompletely. Other metabolic changes induced by ischemia were attenuated by d-cis-diltiazem but not by l-cis-diltiazem. In heart pretreated with d-cis- or l-cis-diltiazem, both the mechanical function and the levels of metabolites recovered during reperfusion, the degree of recovery with both drugs being similar. These results indicate that not only d-cis-diltiazem but also l-cis-diltiazem has an anti-ischemic action probably due to inhibition of the tissue NEFA accumulation. These results also suggest that the mechanism of the protective effect of d-cis-diltiazem on the ischemic myocardium is not entirely due to the calcium channel-blocking action. Treatment with low Ca2+ (1.0 mM CaCl2) also attenuated the ischemia-induced changes. The interval between reoxygenation and start of function in the reperfused heart that had been treated with low Ca2+ was significantly longer than that with d-cis- or l-cis-diltiazem. The effect of these isomers to shorten this interval may contribute to their common anti-ischemic action.
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PMID:Both d-cis- and l-cis-diltiazem have anti-ischemic action in the isolated, perfused working rat heart. 224 48

The brain damage that evolves from perinatal cerebral hypoxia-ischemia may involve lingering disturbances in metabolic activity that proceed into the recovery period. To clarify this issue, we determined the carbohydrate and energy status of cerebral tissue using enzymatic, fluorometric techniques in an experimental model of perinatal hypoxic-ischemic brain damage. Seven-day postnatal rats were subjected to unilateral common carotid artery ligation followed by 3 h of hypoxia with 8% oxygen at 37 degrees C. This insult is known to produce tissue injury (selective neuronal necrosis or infarction) predominantly in the cerebral hemisphere ipsilateral to the carotid artery occlusion in 92% of the animals. Rat pups were quick-frozen in liquid nitrogen at 0, 1, 4, 12, 24, or 72 h of recovery; littermate controls underwent neither ligation nor hypoxia. Glucose in both cerebral hemispheres was nearly completely exhausted during hypoxia-ischemia, with concurrent increases in lactate to 10 mmol/kg. During recovery, glucose promptly increased above control values, suggesting an inhibition of glycolytic flux, as documented in the ipsilateral cerebral hemisphere by measurement of glucose utilization (CMRglc) at 24 h. Tissue lactate declined rapidly during recovery but remained slightly elevated in the ipsilateral hemisphere for 12 h. Phosphocreatine (P approximately Cr) and ATP in the ipsilateral cerebral hemisphere were 14 and 26% of control (p less than 0.001) at the end of hypoxia-ischemia; total adenine nucleotides (ATP + ADP + AMP) also were partially depleted (-46%).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Carbohydrate and energy metabolism during the evolution of hypoxic-ischemic brain damage in the immature rat. 230 39

The catabolism of adenine nucleotides (AdN) in rat soleus muscle (predominantly slow twitch) is very different from that in fast-twitch muscle. AMP deaminase is highly inhibited during brief (3 min) intense (120 tetani/min) in situ stimulation, resulting in little inosine 5'-monophosphate (IMP) accumulation (0.21 mumol/g). Even with ligation of the femoral artery during the same brief intense contraction conditions there is surprisingly little increase in IMP (0.37 mumol/g), although AdN depletion is evident (-1.30 mumol/g). We have tested the hypothesis that accumulation of purine nucleosides and bases accounts for the AdN depletion by measuring purine degradation products using high-performance liquid chromatography. There was no stoichiometric accumulation of purine degradation products to account for the observed AdN depletion even though metabolite recovery was essentially quantitative. We hypothesis that under these conditions AdN are converted to a form different from purine nucleoside and base degradation products. In contrast to the inhibition of AMP deamination seen during brief ischemia, slow-twitch muscle depletes a substantial fraction (28%) of muscle AdN (1.75 mumol/g) that can be accounted for stoichiometrically as purine degradation products during an extended 10-min ischemic period of mild (12 tetani/min) contraction conditions. IMP accumulation (1 mumol/g) is most prominent with inosine, accounting for 23% (0.4 mumol/g) of the depleted AdN, showing that slow-twitch red muscle is capable of both AMP deamination and the subsequent production of purine nucleosides during an extended period of ischemic contractions. The present results indicate that AdN metabolism in the soleus muscle is complex, yielding expected degradation products or a loss of total purines, depending on contraction conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Adenine nucleotide degradation in slow-twitch red muscle. 230 68

An in vivo rat hindlimb tourniquet ischemia model was used to study the purine nucleotide metabolism in response to 2, 4, and 6 h of ischemia and to the same ischemia periods followed by 1 h of reperfusion. All purine intermediates from ATP to uric acid were determined in skeletal muscle with a high-performance liquid chromatography (HPLC) system. The major metabolic event during ischemia is to temporarily save the nucleotide pool as inosine-5'-monophosphate (IMP. On restitution of the circulation as the energy state recovers, the IMP is converted back to AMP via the purine nucleotide cycle. Six hours of ischemia is associated with irreversible damage and no recovery fo the adenine nucleotides on reperfusion. Fast-twitch muscles appear to be more susceptible than slow-twitch muscles in response to ischemia and reperfusion. A severalfold increase of intracellular hypoxanthine occurred during ischemia, whereas uric acid formation is observed only after reperfusion. These findings are discussed in relation to the proposed role of xanthine oxidase, as an enzyme generating tissue-injurious oxygen free radicals.
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PMID:Purine metabolism after in vivo ischemia and reperfusion in rat skeletal muscle. 236 Jun 63

The effect of allopurinol was studied in a normothermic liver ischemia rat model. Functional (bile flow) and biochemical parameters (high-energy phosphates, ATP, ADP, AMP), energy charge, hypoxanthine and xanthine were determined prior to and during 60 min of ischemia followed by 120 min of reperfusion. Allopurinol given in the preischemic period (50%) and as a bolus (50%) prior to reperfusion improved liver function significantly, whereas allopurinol given in the preischemic period (50%) and after start of reperfusion (50%) had no effect. The data indicates that allopurinol given prior to reperfusion saved hypoxanthine which was used for ATP resynthesis during reperfusion.
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PMID:60 min normothermic liver ischemia in rats: allopurinol improves energy status and bile flow during reperfusion. 237 23

Sudden induction of ischemia by occlusion of a major branch of a coronary artery in mammalian heart sets into motion a series of events that culminates in the death of markedly ischemic myocytes. The changes begin within 8-10 seconds of occlusion and include 1) cessation of aerobic metabolism, 2) depletion of creatine phosphate, 3) onset of anaerobic glycolysis (AG), and 4) accumulation of products of anoxic metabolism in the ischemic tissue. Functional defects appear simultaneously, including depressed contractile activity and electrocardiographic changes. The demand of the ischemic myocytes for energy exceeds the supply of high-energy phosphate (approximately P) possible from AG; as a consequence, myocyte adenosine diphosphate increases, and adenylate kinase is activated to capture the approximately P bond of adenosine diphosphate. Adenosine monophosphate is a product of this reaction; it accumulates and is progressively degraded to nucleosides and bases that are lost from the myocyte. The pace of development of the short-term metabolic changes slows after 40-60 minutes of ischemia, at which time most of the severely ischemic myocytes are irreversibly injured. Early in the irreversible phase of injury tissue is characterized as follows by: 1) very low approximately P content (creatine phosphate less than 1-2% and adenosine triphosphate less than 10% of control), 2) a depressed adenine nucleotide pool that consists principally of adenosine monophosphate, 3) virtual cessation of AG, 4) low pH and low glycogen content, 5) high inosine and hypoxanthine contents, 6) a markedly increased osmolar load consisting chiefly of lactate, and 7) characteristic ultrastructural changes including cell swelling and evidence of generalized mitochondrial and marked sarcolemmal damage. Sarcolemmal disruption is the feature that we hypothesize causes irreversibility; however, its pathogenesis is unknown.
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PMID:Development of cell injury in sustained acute ischemia. 239 18

Adenylate cyclase (AC) function was studied in homogenate and particulate preparations of ischemic rat heart obtained from three models: anoxic-ischemic incubations, coronary artery ligation, and global low-flow perfusion of isolated hearts. Both basal activity and the function of AC measured in the presence of NaF (8 X 10(-3)M), Gpp(NH)p (10(-5)M), and L-(-)-isoprenaline (10(-8)-10(-4)M) were reduced to 50% of the control value in homogenates of hearts incubated under anoxic-ischemic conditions for 10 min. Comparable results were obtained with homogenates from the ischemic area 20 min after coronary artery ligation in anesthetized open-chest rats with artificial ventilation. Reduced AC activity of the anoxic-ischemic hearts was completely reversible by aerobic reperfusion, provided the ischemic period did not exceed 20 min. AC activity in homogenates of isolated hearts perfused at low-flow was not changed, indicating a nonuniform alteration of AC system in nonperfused and low-flow perfused areas of the ischemic heart. Depression of myocardial AC function during severe ischemia was avoided by reducing Ca2+ in the incubation buffer, in combination with addition of EGTA during the homogenization step, and by pretreating the animals with verapamil. It is suggested that the depressed AC function is caused mainly by an increase in intracellular Ca2+, which inhibits the enzyme at its catalytic site. A negative feedback control of AC function by Ca2+ is postulated that may operate especially in the ischemic myocardium.
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PMID:Reversible inhibition of adenylate cyclase activity in the ischemic myocardium. 241 Jul 31

The endogenous level of epidermal cyclic AMP does not remain constant but increases rapidly and transiently after removal of the tissue; this is known as the "ischemia" effect. UVB-irradiated epidermis which shows increased beta-adrenergic response revealed an increased ischemia effect, while psoriatic involved epidermis which shows decreased beta-adrenergic response revealed a decreased ischemia effect. Because of the similar rise-and-fall pattern between the ischemia effect and the beta-adrenergic response, the mechanism of the ischemia effect was investigated, especially in terms of the beta-adrenergic relationship. The ischemic rise of epidermal cyclic AMP was well preserved after 6 h pretreatment at 4 degrees C, and, following the pretreatment, the skin markedly increased its cyclic AMP level by the 37 degrees C treatment with 1 mM isobutylmethyl xanthine. The addition of propranolol or cimetidine at the time of 37 degrees C treatment (following the 4 degrees C pretreatment) had no effect on the ischemia effect; both skin groups markedly increased their cyclic AMP levels to an extent similar to that of the control skin. However, the addition of propranolol at the time of both preincubation (at 4 degrees C) and incubation (at 37 degrees C) markedly decreased the ischemic rise of cyclic AMP. Similar treatment by cimetidine had no effect on the ischemia effect. There was no significant difference in cyclic AMP phosphodiesterase activities among skin groups by propranolol or cimetidine pretreatment. These results indicate that the so-called ischemic rise of epidermal cyclic AMP is actually the beta-adrenergic adenylate cyclase-dependent process. Our results also indicate that the magnitude of the "ischemic" rise of cyclic AMP is generally parallel to the beta-adrenergic responsiveness of epidermis.
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PMID:"Ischemic" rise of epidermal cyclic AMP is a beta-adrenergic adenylate cyclase-dependent process. 242 5

The protective effect of calcium antagonists on ischemic heart has been attributed to decreased energy expenditure. We administered one of the newer calcium antagonists, DL-bepridil (0.1-10 microM), to Langendorff rat hearts 10 or 15 min before ischemia (flow reduction approximately 80%). Vasodilation during normoxia was already observed with 0.3 microM DL-bepridil (flow increase 34%, p less than 0.005). This concentration decreased normoxic contractility and ischemic purine release, a marker for ATP breakdown. In the absence of bepridil, purine release of hearts that were made ischemic was 8.5-fold higher than that of normoxic control hearts. With 1 microM bepridil, the ischemic purine efflux was suppressed by 55% (p less than 0.05), with negative inotropy (p greater than 0.05) during normoxia. At 3 and 10 microM, bepridil decreased normoxic contractility by 40 and 75%, respectively (p less than 0.001), concomitant with a decrease in ischemic purine release by 80 and 76%, respectively (p less than 0.01). At the end of ischemia, myocardial ATP and creatine phosphate had decreased by 22 and 55%, respectively (p less than 0.05), and ADP, AMP, and creatine had increased 1.5-3.5-fold (p less than 0.05). Bepridil (3 microM) normalized the adenine nucleotide values; creatine and creatine phosphate approached control levels. The dose-dependent protection of the ischemic heart by bepridil appears to arise from its negative inotropic action during normoxia.
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PMID:Protection by bepridil against myocardial ATP-catabolism is probably due to negative inotropy. 244 Nov 54

Delayed afterdepolarizations (DADs) are Ca++-dependent electrophysiological abnormalities, which are evoked by a variety of conditions that induce intracellular Ca++ overload, including fast pacing, isoproterenol, dibutyryl cyclic AMP, and intracellular injection of Ca++. Since Ca++ overload is suspected of playing a role in both ischemic and reperfusion cellular damage, a reasonable hypothesis would be that DADs could play a role in ischemic or reperfusion arrhythmias. No direct proof has, however, been obtained for such a role for DADs. We propose that DADs could be associated with arrhythmias in which there is Ca++ overload of sufficient magnitude to cause an increased oscillatory release of Ca++ from the sarcoplasmic reticulum (SR), provided energy is available in the form of ATP. A sustained increase of Ca++ is likely to reflect energy depletion and therefore exclude a significant contribution of DADs to arrhythmia development. Thus, DADs are more likely to play a role in: (i) reperfusion arrhythmias and (ii) arrhythmias arising in moderately ischemic tissue, than in severe ischemia with marked energy depletion.
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PMID:Proposed role of energy supply in the genesis of delayed afterdepolarizations--implications for ischemic or reperfusion arrhythmias. 244 88


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