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- Ahlström, Katarina, 1966
(författare)
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Energy-metabolic aspects of ischemia and pre-treatment: studies in porcine myocardium
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of this thesis is to clarify mechanisms involved in protective pre-treatment of ischemia by carbon monoxide (CO) and ischemic preconditioning (IP), so that new pro-tective therapies can be designed. This is studied in heart muscle, where the clinical gain would ultimately be to be able to prolong the period during a threatened myocardial infarction where permanent injury can be prevented. The aim is to elucidate energy meta-bolic relations as a basis for temporary metabolic adaptation to threatened injury in heart muscle, with focus on the biological relevance of this mechanism. All studies were conducted in an open-chest, anesthetized pig model using microdialysis sampling. Methods: In anesthetized 40 kg pigs, regional myocardial ischemia was produced by transient snare-ligation of a branch of the left anterior descending coronary artery. Micro-dialysis catheters were used for local sampling of interstitial fluid in the ischemic area. In Studies 1 and 2, CO was administered before prolonged ischemia in a clinically relevant dose (5% increase in carboxyhemoglobin). In Study 2, 45Ca2+ was administered locally by microperfusate to ischemic myocardium with 45Ca2+ recovery used as a marker for intra-cellular calcium overload during ischemia. Myocardial injury markers glycerol and glut-amate (and taurine in Studies 3 and 4) were measured in microdialysate. In Studies 3 and 4, IP was performed by 4 brief transient cycles of coronary occlusion and reperfusion before a prolonged index ischemic episode was performed. In Study 3, 14C-marked adenosine was administered locally via microdialysis catheters in the heart muscle wall, and when this was metabolized during ischemia as an energy source, it was detected as 14C-marked lactate. In Study 4, a water-soluble purine nucleoside phosphorylase inhibitor was administered to heart muscle via microdialysis which was treated by IP before an index ischemia. Markers of glycolysis were measured serially before and during ischemia for Studies 1-4. Radio-labelled markers were analyzed using liquid chromatography and scintigraphy. Results: Study 1 results showed clear signs of metabolic advantage as far as glycolytic markers related to CO during myocardial ischemia. Study 2 results demonstrated no apparent energy metabolic advantage including for 45Ca2+ recovery and no diminishment of injury markers related to the single tested carbon monoxide dose during ischemia. Study 3 showed that IP led to enhanced radio-marked adenosine consumption as an energy-metabolic substrate, and that glycolytic flow (as less glucose consumption and lactate formation) was slower in IP-treated heart muscle. Study 4 showed that local purine nucleoside phosphorylase blockade inhibits adenosine utilization as an energy-metabolic substrate during ischemia, but this did not have an effect on glycolysis or injury markers during prolonged ischemia after IP. Conclusions: From Studies 1 and 2, we concluded that CO in this dose could show effects on glycolysis during ischemia but does not seem to confer cell protection during ischemia or early reperfusion, though CO protective effects in other doses or time frames cannot be ruled out. From Study 3 we concluded that there may be an immediate energy-metabolic explanation for why more IP-treated cells survive during prolonged ischemia. From Study 4 we concluded that experimental purine nucleoside phosphorylase blockade appears to allow interruption of IP-related adenosine utilization as an energy-metabolic substrate during prolonged ischemia without obvious effects on glycolysis, and that this requires further study to test if adenosine as an energy resource during ischemia is associated with protection during infarction. Key words: myocardial ischemia, preconditioning, carbon monoxide, adenosine
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- Ahlström, Katarina, 1966, et al.
(författare)
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Exogenous carbon monoxide does not affect cell membrane energy availability assessed by sarcolemmal calcium fluxes during myocardial ischaemia-reperfusion in the pig
- 2011
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Ingår i: European Journal of Anaesthesiology. - 0265-0215 .- 1365-2346. ; 28:5, s. 356-362
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Tidskriftsartikel (refereegranskat)abstract
- Carbon monoxide is thought to be cytoprotective and may hold therapeutic promise for mitigating ischaemic injury. The purpose of this study was to test low-dose carbon monoxide for protective effects in a porcine model of acute myocardial ischaemia and reperfusion. In acute open-thorax experiments in anaesthetised pigs, pretreatment with low-dose carbon monoxide (5% increase in carboxyhaemoglobin) was conducted for 120 min before localised ischaemia (45 min) and reperfusion (60 min) was performed using a coronary snare. Metabolic and injury markers were collected by microdialysis sampling in the ventricular wall. Recovery of radio-marked calcium delivered locally by microperfusate was measured to assess carbon monoxide treatment effects during ischaemia/reperfusion on the intracellular calcium pool. Coronary occlusion and ischaemia/reperfusion were analysed for 16 animals (eight in each group). Changes in glucose, lactate and pyruvate from the ischaemic area were observed during ischaemia and reperfusion interventions, though there was no difference between carbon monoxide-treated and control groups during ischaemia or reperfusion. Similar results were observed for glycerol and microdialysate Ca-45(2+) recovery. These findings show that a relatively low and clinically relevant dose of carbon monoxide did not seem to provide acute protection as indicated by metabolic, energy-related and injury markers in a porcine myocardial ischaemia/reperfusion experimental model. We conclude that protective effects of carbon monoxide related to ischaemia/reperfusion either require higher doses of carbon monoxide or occur later after reperfusion than the immediate time frame studied here. More study is needed to characterise the mechanism and time frame of carbon monoxide-related cytoprotection.
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- Ahlström, Katarina, 1966, et al.
(författare)
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Metabolic responses in ischemic myocardium after inhalation of carbon monoxide.
- 2009
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Ingår i: Acta Anaesthesiol Scand. - : Wiley. - 1399-6576 .- 0001-5172. ; 53:8, s. 1036-42
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: To clarify the mechanisms of carbon monoxide (CO) tissue-protective effects, we studied energy metabolism in an animal model of acute coronary occlusion and pre-treatment with CO. METHODS: In anesthetized pigs, a coronary snare and microdialysis probes were placed. CO (carboxyhemoglobin 5%) was inhaled for 200 min in test animals, followed by 40 min of coronary occlusion. Microdialysate was analyzed for lactate and glucose, and myocardial tissue samples were analyzed for adenosine tri-phosphate, adenosine di-phosphate, and adenosine mono-phosphate. RESULTS: Lactate during coronary occlusion was approximately half as high in CO pre-treated animals and glucose levels decreased to a much lesser degree during ischemia. Energy charge was no different between groups. CONCLUSIONS: CO in the low-doses tested in this model results in a more favorable energy metabolic condition in that glycolysis is decreased in spite of maintained energy charge. Further work is warranted to clarify the possible mechanistic role of energy metabolism for CO protection.
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- Waldenström, Anders, et al.
(författare)
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Ischaemic preconditioning reduces myocardial calcium overload in coronary-occluded pig hearts shown by continuous in vivo assessment using microdialysis.
- 2012
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Ingår i: Clinical physiology and functional imaging. - Malden, MA : Wiley-Blackwell. - 1475-097X .- 1475-0961. ; 32:2, s. 133-8
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Tidskriftsartikel (refereegranskat)abstract
- During ischaemia, ATP depletion leads to insufficient fuelling for Na(+) /K(+) ATPase, decreased electrochemical potential and increased influx of calcium ions. This study demonstrated a means to assess the effects of ischaemic preconditioning (IP) on the free intracellular Ca(2+) pool during prolonged ischaemia. In a porcine myocardial ischaemia model, microdialysis (MD) was used for sampling of metabolic and injury markers in IP and non-IP (control) groups. (45) Ca(2+) was delivered in microperfusate locally to ischaemic myocardium, with distribution and uptake assessed by (45) Ca(2+) recovery in microdialysate. Cardiomyocytes in vitro were exposed to a Ca(2+) ionophore and tested for (45) Ca(2+) uptake. An accentuated myocardial calcium ion influx (observed as an increased microdialysate (45) Ca(2+) recovery in the extracellular milieu) was noted in control pigs compared with IP pigs during ischaemia. Suspended cardiomyocytes preincubated with a Ca(2+) ionophore to increase the intracellular calcium ion pool and subsequently incubated with (45) Ca(2+) , displayed lower (45) Ca(2+) uptake in cells compared with control cells not exposed to the ionophore, corroborating the idea of a strong relationship between degree of intracellular calcium overload and microdialysate (45) Ca(2+) recovery. The ischaemic insult was differentially verified by metabolic and injury markers. We introduce an in vivo method for serial assessment of myocardial calcium overload during ischaemia, using a MD technique and (45) Ca(2+) inclusion. IP leads to relatively less calcium overload as assessed by this new method, and we interpret this to mean that reduction in calcium overload is an important part of the IP protective effect.
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