Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0001127 (respiratory acidosis)
 1,501 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During regional ischemia gradients of extracellular potassium concentration ([K+]o) and extracellular pH (pHo) exist. In globally ischemic papillary muscles increased PCO2 causes a rise in [K+]o. We studied whether pHo and [K+]o are causally related during acute regional ischemia in the isolated blood-perfused pig heart. Multiple pH- or K(+)-sensitive electrodes were inserted in the left ventricular midmyocardium. Local electrograms and ionic data were simultaneously acquired. Regional ischemia was produced by interrupting left anterior descending (LAD) artery flow (10 min). Up to 5 mm from the electrophysiological border the pH-K relation deviated from that in the central ischemic zone. Respiratory acidosis (pH about 7.10) of the perfusate in the presence of LAD-ischemia caused acidification of the ischemic border zone without a local change in [K+]o. We conclude that pHo changes are not related to changes of intramural [K+]o in the lateral border zone during regional ischemia.
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PMID:The relation between extracellular potassium concentration and pH in the border zone during regional ischemia in isolated porcine hearts. 852 66

The purpose of this study was to examine whether initial acidic reperfusion after ischemia followed by stepwise normalization of perfusate pH could improve functional recovery and to assess whether this is associated with a reduction in Ca2+ overload. Isolated rat hearts were subjected to global ischemia for 25 min, followed by 30 min of reperfusion. In the control group (Group C), the perfusate pH was 7.4 throughout reperfusion. In the acidic groups, the perfusate pH was 6.8 for the first 5 min, 7.1 for the second 5 min, and 7.4 for the remainder of reperfusion. Acidic buffer was produced either by adding HCl (metabolic acidosis, Group MA) or by bubbling with gas containing 12 to 24% CO2 (respiratory acidosis, Group RA). The recovery of ventricular function, Ca2+ uptake, and energy metabolites were analyzed. Thirteen of the 15 hearts in Group C, 14 of the 15 in MA and 8 of the 15 in RA recovered regular cardiac rhythm at the end of reperfusion. In these hearts which exhibited normal rhythm, the percent recovery in developed pressure was higher (MA: 73 +/- 8, RA: 68 +/- 6, C: 51 +/- 5%, p < 0.05) and left ventricular end-diastolic pressure was lower (MA: 5.1 +/- 1.4, RA: 5.9 +/- 1.3, C: 14.2 +/- 2.7 mmHg, p < 0.05) in the acidic groups. The improved recovery was associated with a significant reduction in Ca2+ uptake which persisted with the restoration of normal pH. These results demonstrate that early acidic reperfusion enhances contractile recovery and diminishes Ca2+ overload. Moreover, these salutary effects are maintained after stepwise normalization of the perfusate pH to physiological values.
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PMID:Effect of stepwise normalization of perfusate pH on post-ischemic functional recovery and Ca2+ overload in isolated rat hearts. 890 86

Myocardial ischemia, primarily a metabolic insult, is also defined by altered cardiac mechanical and electrical activity. We have investigated the metabolic contributions to the electrophysiological changes during low-flow ischemia (7.5% of the control flow) using 31P NMR spectroscopy to monitor metabolic parameters, suction electrodes to study epicardial monophasic action potentials, and 86Rb as a tracer for K+-equivalent efflux during low-flow ischemia in the Langendorff-perfused ferret heart. Shortening of the action potential duration at 90% repolarization (APD90) was most marked between 1 and 5 min after induction of ischemia, at which time it shortened from 261 +/- 4 to 213 +/- 8 ms. The period of marked APD90 shortening was accompanied by a fivefold increase in the rate of 86Rb efflux, both of which were inhibited by the ATP-sensitive K+ (KATP)-channel blockers glibenclamide and 5-hydroxydecanoate (5-HD), as well as by a significant fall in intracellular pH (pHi) from 7.14 +/- 0.02 to 6.83 +/- 0.03 but no change in intracellular ATP concentration ([ATP]i). We therefore investigated whether a fall in pHi could be the metabolic change responsible for modulating cardiac KATP channel activity in the intact heart during ischemia. Both metabolic (30 mM lactate added to extracellular solution) and respiratory (PCO2 increased to 15%) acidosis caused an initial lengthening of APD90 to 112 +/- 1.5 and 113 +/- 0.9%, respectively, followed by shortening during continued acidosis to 106 +/- 1.2 and 106 +/- 1.4%, respectively. The shortening of APD90 during continued acidosis was inhibited by glibenclamide, consistent with acidosis causing activation of KATP channels at normal [ATP]i. The similar responses to metabolic (induced by adding either l- or d-lactate) and respiratory acidosis suggest that lactate has no independent metabolic effect on action potential repolarization.
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PMID:Changes in ventricular repolarization during acidosis and low-flow ischemia. 968 44

Relative hypoventilation, involving passively-or "permissively"-generated hypercapnic acidosis (HCA), may improve outcome by reducing ventilator-induced lung injury. However, the effects of HCA per se on pulmonary microvascular permeability (Kf,c) in noninjured or injured lungs are unknown. We investigated the effects of HCA in the isolated buffer-perfused rabbit lung, under conditions of: (1) no injury; (2) injury induced by warm ischemia-reperfusion; and (3) injury induced by addition of purine and xanthine oxidase. HCA (fraction of inspired carbon dioxide [FICO2] 12%, 25% versus 5%) had no adverse microvascular effects in uninjured lungs, and prevented (FICO2 25% versus 5%) the increase in Kf,c following warm ischemia-reperfusion. HCA (FICO2 25% versus 5%) reduced the elevation in Kf,c, capillary (Pcap), and pulmonary artery (Ppa) pressures in lung injury induced by exogenous purine/xanthine oxidase; inhibition of endogenous NO synthase in the presence of 25% FICO2 had no effect on Kf,c, but attenuated the reduction of Pcap and Ppa. HCA inhibited the in vitro generation of uric acid from addition of xanthine oxidase to purine. We conclude that in the current models, HCA is not harmful in uninjured lungs, and attenuates injury in free-radical-mediated lung injury, possibly via inhibition of endogenous xanthine oxidase.
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PMID:Hypercapnic acidosis may attenuate acute lung injury by inhibition of endogenous xanthine oxidase. 981 11

Hypoventilation, associated with hypercapnic acidosis (HCA), may improve outcome in acute lung injury (ALI). We have recently reported that HCA per se protects against ALI. The current study explored whether the mechanisms of protection with HCA were related to acidosis versus hypercapnia. Because CO(2) equilibrates rapidly across cell membranes, we hypothesized that (1) HCA would afford greater protection than metabolic acidosis. We further hypothesized that (2) buffering HCA would attenuate its protection. Forty isolated perfused rabbit lung preparations were randomized to: control (normal pH, PCO(2)); HCA; metabolic acidosis; or buffered hypercapnia. After ischemia-reperfusion (IR) injury wet:dry ratio was greatest with control and buffered hypercapnia, and rank order of capillary filtration coefficient was: control approximately buffered hypercapnia > metabolic acidosis > HCA. Isogravimetric pressure reduction was greatest with buffered hypercapnia. Despite comparable injury, pulmonary artery pressure elevation was less with buffered hypercapnia versus control. In vitro xanthine oxidase (XO) activity depended on pH, not PCO(2). We conclude that: (1) HCA and metabolic acidosis are protective, but HCA is the most protective; (2) buffering HCA attenuates its protection; (3) buffering HCA causes pulmonary vasodilation; (4) because metabolic acidosis and HCA similarly inhibit in vitro XO activity, the differential effects cannot be explained solely on the basis of extracellular XO activity.
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PMID:Buffering hypercapnic acidosis worsens acute lung injury. 1061 11

The contribution of acidosis to the development of reperfusion injury is controversial. In this study, we examined the effects of respiratory acidosis and hypoxia in a frequently used in vivo liver ischemia and reperfusion (I/R) injury rat model. Rats were anesthetized with intraperitoneal anesthetics and subjected to partial liver ischemia (70%) for 60 min and subsequent reperfusion for 90 min under the following conditions: 1) no acidosis and normoxia, maintained by controlled ventilation; 2) acidosis and normoxia, maintained by passive supply with oxygen; 3) no acidosis and hypoxia, maintained by bicarbonate administration without respiratory support; and 4) acidosis and hypoxia, i.e., without respiratory support or pH correction. Changes in plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured as parameters of hepatocellular injury, and bile secretion was monitored. AST and ALT levels were lowest in the ventilated rats and highest in the bicarbonate-treated rats. No differences in bile secretion were found between groups. Our results suggest that respiratory acidosis significantly enhanced liver I/R injury under normoxic conditions, whereas respiratory acidosis significantly reduced liver I/R injury under hypoxic conditions.
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PMID:Influence of acidosis and hypoxia on liver ischemia and reperfusion injury in an in vivo rat model. 1207 Feb 20

Deliberate induction of prophylactic hypercapnic acidosis protects against lung injury after in vivo ischemia-reperfusion and ventilation-induced lung injury. However, the efficacy of hypercapnic acidosis in sepsis, the commonest cause of clinical acute respiratory distress syndrome, is not known. We investigated whether hypercapnic acidosis--induced by adding CO2 to inspired gas--would be protective against endotoxin-induced lung injury in an in vivo rat model. Prophylactic institution of hypercapnic acidosis (i.e., induction before endotoxin instillation) attenuated the decrement in arterial oxygenation, improved lung compliance, and attenuated alveolar neutrophil infiltration compared with control conditions. Therapeutic institution of hypercapnic acidosis, that is, induction after endotoxin instillation, attenuated the decrement in oxygenation, improved lung compliance, and reduced alveolar neutrophil infiltration and histologic indices of lung injury. Therapeutic hypercapnic acidosis attenuated the endotoxin-induced increase in the higher oxides of nitrogen and nitrosothiols in the lung tissue and epithelial lining fluid. Lung epithelial lining fluid nitrotyrosine concentrations were increased with hypercapnic acidosis. We conclude that hypercapnic acidosis attenuates acute endotoxin-induced lung injury, and is efficacious both prophylactically and therapeutically. The beneficial actions of hypercapnic acidosis were not mediated by inhibition of peroxynitrite-induced nitration within proteins.
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PMID:Hypercapnic acidosis attenuates endotoxin-induced acute lung injury. 1469 4

The sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a) is under the control of an SR protein named phospholamban (PLN). Dephosphorylated PLN inhibits SERCA2a, whereas phosphorylation of PLN at either the Ser16 site by PKA or the Thr17 site by CaMKII reverses this inhibition, thus increasing SERCA2a activity and the rate of Ca2+ uptake by the SR. This leads to an increase in the velocity of relaxation, SR Ca2+ load and myocardial contractility. In the intact heart, beta-adrenoceptor stimulation results in phosphorylation of PLN at both Ser16 and Thr17 residues. Phosphorylation of the Thr17 residue requires both stimulation of the CaMKII signaling pathways and inhibition of PP1, the major phosphatase that dephosphorylates PLN. These two prerequisites appear to be fulfilled by beta-adrenoceptor stimulation, which as a result of PKA activation, triggers the activation of CaMKII by increasing intracellular Ca2+, and inhibits PP1. Several pathological situations such as ischemia-reperfusion injury or hypercapnic acidosis provide the required conditions for the phosphorylation of the Thr17 residue of PLN, independently of the increase in PKA activity, i.e., increased intracellular Ca2+ and acidosis-induced phosphatase inhibition. Our results indicated that PLN was phosphorylated at Thr17 at the onset of reflow and immediately after hypercapnia was established, and that this phosphorylation contributes to the mechanical recovery after both the ischemic and acidic insults. Studies on transgenic mice with Thr17 mutated to Ala (PLN-T17A) are consistent with these results. Thus, phosphorylation of the Thr17 residue of PLN probably participates in a protective mechanism that favors Ca2+ handling and limits intracellular Ca2+ overload in pathological situations.
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PMID:The importance of the Thr17 residue of phospholamban as a phosphorylation site under physiological and pathological conditions. 1664 92

Returning to normal pH after acidosis, similar to reperfusion after ischemia, is prone to arrhythmias. The type and mechanisms of these arrhythmias have never been explored and were the aim of the present work. Langendorff-perfused rat/mice hearts and rat-isolated myocytes were subjected to respiratory acidosis and then returned to normal pH. Monophasic action potentials and left ventricular developed pressure were recorded. The removal of acidosis provoked ectopic beats that were blunted by 1 muM of the CaMKII inhibitor KN-93, 1 muM thapsigargin, to inhibit sarcoplasmic reticulum (SR) Ca(2+) uptake, and 30 nM ryanodine or 45 muM dantrolene, to inhibit SR Ca(2+) release and were not observed in a transgenic mouse model with inhibition of CaMKII targeted to the SR. Acidosis increased the phosphorylation of Thr(17) site of phospholamban (PT-PLN) and SR Ca(2+) load. Both effects were precluded by KN-93. The return to normal pH was associated with an increase in SR Ca(2+) leak, when compared with that of control or with acidosis at the same SR Ca(2+) content. Ca(2+) leak occurred without changes in the phosphorylation of ryanodine receptors type 2 (RyR2) and was blunted by KN-93. Experiments in planar lipid bilayers confirmed the reversible inhibitory effect of acidosis on RyR2. Ectopic activity was triggered by membrane depolarizations (delayed afterdepolarizations), primarily occurring in epicardium and were prevented by KN-93. The results reveal that arrhythmias after acidosis are dependent on CaMKII activation and are associated with an increase in SR Ca(2+) load, which appears to be mainly due to the increase in PT-PLN.
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PMID:Increased intracellular Ca2+ and SR Ca2+ load contribute to arrhythmias after acidosis in rat heart. Role of Ca2+/calmodulin-dependent protein kinase II. 1872 72

Acute rhabdomyolysis is a syndrome characterized by the lesion of skeletal muscle resulting in subsequent release of intracellular contents into the circulatory system, which can cause potentially lethal complications. These contents include myoglobin, creatine phosphokinase, potassium, aldolase, lactate dehydrogenase and glutamic-oxaloacetic transaminase. There are numerous causes that can lead to acute rhabdomyolysis and many of patients present with multiple causes. The most common potentially lethal complication of rhabdomyoloysis is acute renal failure. In this article we present a case of a patient that developed clinical signs of acute rhabdomyolysis after consumption of heroin and alcohol. After approximately nine hours of alcohol and heroin induced coma he had acute compartment syndrome of the right arm, and clinical and laboratory signs of acute rhabdomyolysis with acute renal failure as a complication of rhabdomyolysis. Acute rhabdomyolysis developed in the patient as the result of acute compartment syndrome, with direct toxic activity of alcohol and diamorphine. During the period of coma, due to lying in particular position over a long period of time, pressure upon the certain part of the body caused muscle compression and capillary occlusion in fascial compartments, which led to ischemia. Upon pressure relief and beginning of tissue recovery, post ischemic compartment syndrome occurred with subsequent rhabdomyolysis. Getting out of coma the patient started to complain of severe pain in the right arm, which clinically worsened on passive stretching of the limb, with the loss of sensation and weakness. Laboratory findings showed high levels of creatine phosphokinase as the most sensitive marker of muscular damage. The peak of creatine phosphokinase level can be predictive for the development of acute renal failure because myoglobin level may return to normal within 6 hours after muscle injury. The peak of creatine phosphokinase (186.080 U/L; normal range 0-177) was recorded at 12 hours of admission. Other pertinent laboratory results such as urea, creatinine, prothrombin time, alanine aminotransferase and aspartate aminotransferase were also changed significantly. The peak of potassium level before dialysis was 6.8 mmol/L. Emergency fasciotomy of the anterior and posterior compartment syndrome was performed by a team of physicians after clinical examination. The second look debridement was performed at 48 and 72 hours. The plastic surgical procedure was performed 4 weeks later. On admission the patient also had oliguria with dark brown pigment in his urine. Arterial blood gases revealed metabolic and respiratory acidosis. The patient was hypovolemic and IV rehydratation with crystalloids, sodium bicarbonate and mannitol started immediately upon admission. Despite therapy his urine output decreased. Hemodialysis was initiated at serum potassium level of 6.8 mm/L and continued until his urine output returned to normal in three weeks. The patient was discharged from the hospital after six weeks, with normal urine output, without functional abnormality in his upper right limb. Acute rhabdomyolysis should be considered as a possibility in any patient with prolonged imobilization while in coma as well as in any intoxicated patient. Of course, creatine phosphokinase is the most sensitive indicator of muscle injury and the degree of creatine phosphokinase elevation correlates with the amount of muscle injury and disease severity. Other laboratory findings can help identify common complications of rhabdomyolysis such as acute renal failure, metabolic derangements and disseminated intravascular coagulopathy.
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PMID:[Acute rhabdomyolysis: a case report and literature review]. 1884 54


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