Showing papers by "Luc Rochette published in 1999"
TL;DR: It is shown that pyruvate could prevent reperfusion injuries in the isolated heart, probably by its antioxidative properties, and the application of pyruVate may contribute to the preservation of hearts for organ transplantation.
Abstract: Formation of oxygen free radicals during heart transplantation seems to be related to the alterations occurring during ischemia and reperfusion and could explain the short preservation time of donor hearts The aim of our study was (a) to analyze the protective effects of pyruvate during cold cardioplegia and ischemia/reperfusion sequence, and (b) to investigate in vitro the radical scavenging properties of this compound After 30 min of perfusion, isolated working rat hearts were arrested by cardioplegic solution, stored 4 h in B21 solutions at 4 degrees C, and reperfused with Krebs-Henseleit buffer for 45 min Pyruvate (2 mM) was added to Krebs-Henseleit, cardioplegic, and storage solutions, and functional parameters were recorded throughout the experiments In a second part, control hearts and hearts treated with pyruvate were cannulated via the aorta and perfused for 30 min by the Langendorff method, arrested by cardioplegic solution, stored 4 h in B21 solutions at 4 degrees C, and reperfused for 45 min by the Langendorff method Malonedialdehyde and alpha-tocopherol levels were determined on heart homogenate In situ detection of apoptotic cells also was performed on tissue samples (left ventricle) at the end of the ischemia/reperfusion sequence To demonstrate in vitro the antioxidant effects of pyruvate, we monitored (a) its hydroxyl radical scavenging properties by using electron paramagnetic resonance (EPR) spectroscopy, and (b) the decrease of fluorescence of allophycocyanin, in the presence of a Fenton system (H2O2/Cu2+) Ischemia for 4 h, followed by myocardial reperfusion, resulted in substantially reduced mechanical function Hearts subjected to this ischemia and pretreated with pyruvate showed a significant improvement in the function recovery After the ischemia/reperfusion protocol, no significant decrease of malonedialdehyde levels was shown on hearts treated with pyruvate However, alpha-tocopherol levels were higher in the pyruvate group compared with the control group At the end of the reperfusion period, levels of apoptotic cells were significantly lower in hearts treated with pyruvate compared with control hearts EPR studies showed that pyruvate was an efficient hydroxyl scavenger, with a median inhibitory concentration (IC50) of 8 mM The allophycocyanin assay also showed a dose-dependent effect of pyruvate against hydroxyl radicals In conclusion, these findings showed that pyruvate could prevent reperfusion injuries in the isolated heart, probably by its antioxidative properties The application of pyruvate may contribute to the preservation of hearts for organ transplantation
103 citations
TL;DR: In this paper, the free radical scavenging properties of aminoguanidine (AG) were examined using the spin-trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO).
Abstract: It is well known that aminoguanidine (AG) can diminish advanced glycosylation of proteins, which might be beneficial in preventing chronic diabetic complications. Recent reports suggested an inter-relationship between glycosylation of protein and free radical damage. In the present study, we examined the free radical scavenging properties of AG. Electron paramagnetic resonance using the spin-trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was performed to determine the superoxide and hydroxyl radical scavenging abilities of AG. These experiments revealed that AG was an effective hydroxyl radical scavenger even though it expressed a direct inhibitory effect on the xanthine oxidase activity at high concentrations (AG ≥ 5 mM). In the second part of the study, allophycocyanin was used as an indicator of free radical mediated protein damage. In the assay, 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) was used as a peroxyl radical generator, and the loss of allophycocyanin fluorescence was monitored. The antioxidant effect of AG was expressed in oxygen-radical absorbing capacity (ORAC), where one ORAC unit equals the net protection produced by I μM Trolox (a water soluble analogue of vitamin E) as a control standard. AG exhibited a significant dose-dependent effect against free radical damage. These radical scavenging properties of AG may contribute to protective effects during glycation and explain the prevention of diabetic complications.
69 citations
TL;DR: It is shown that DXR affected heart reactivity as early as the end of its administration, although irradiation exerted no detectable effect, and different physiopathological mechanisms are involved in heart disturbance at acute and middle terms, IRR and DXR acting on distinct targets without disclosing synergistic effects.
58 citations
TL;DR: The spin-trapping technique allowed us to monitor organ-specific formation of NO after LPS administration and for the first time demonstrated direct NO production in aorta and heart of LPS-treated animals.
Abstract: Summary:The increased production of nitric oxide (NO) has been implicated as the basis for myocardial dysfunction and the lack of response to vasoconstrictors during endotoxin shock induced by lipopolysaccharide (LPS). Our objective was to evaluate and compare NO production in major organs of rats t
25 citations
TL;DR: EDRF exerts a significant inhibition of the hypoxic pulmonary response, SKCa channel activation, EDRF and prostaglandins contribute to the reversal of theHypoxic pressure response, and the vasodilation induced by isoprenaline is mediated in part by activation of KATP channels, that of salbutamol byactivation of KatP channels and EDRf.
Abstract: The aims of this study were to compare, in the rat isolated perfused lung preparation, the antagonist effects of a nonselective β-adrenoceptor agonist (isoprenaline), a selective β2-adrenoceptor agonist (salbutamol) and a selective β3-adrenoceptor agonist (SR 59104A) on the hypoxic pulmonary pressure response, and to investigate the role of K+ channels, endothelium derived relaxing factor and prostaglandins in these effects. K+ channels were inhibited by glibenclamide, charybdotoxin or apamin, NO synthase and cyclo-oxygenase were inhibited by NG-nitro-L-arginine methyl ester (L-NAME) and indomethacin, respectively.
Hypoxic ventilation produced a significant increase in perfusion pressure (+65%, P<0.001) and L-NAME significantly increased this response further (+123%, P<0.01). After apamin, L-NAME, indomethacin, post-hypoxic basal pressure did not return to baseline values (P<0.001).
Glibenclamide partially inhibited the relaxant effects of isoprenaline (P<0.05) and salbutamol (P<0.001) but not that of SR 59104A. In contrast, charybdotoxin and apamin partially inhibited the relaxant effects of SR 59104A (P=0.053 and <0.01, respectively) but did not modify the effects of isoprenaline and salbutamol. L-NAME partially inhibited the dilator response of salbutamol (P<0.01) and SR 59104A (P<0.05) but not that of isoprenaline.
We conclude that (a) EDRF exerts a significant inhibition of the hypoxic pulmonary response, (b) SKCa channel activation, EDRF and prostaglandins contribute to the reversal of the hypoxic pressure response, (c) the vasodilation induced by isoprenaline is mediated in part by activation of KATP channels, that of salbutamol by activation of KATP channels and EDRF. In contrast, SR 59104A partly operates through BKCa, SKCa channels and EDRF activation, differing in this from the β1 and β2-adrenoceptor agonists.
British Journal of Pharmacology (1999) 127, 421–428; doi:10.1038/sj.bjp.0702575
22 citations
TL;DR: The beneficial properties of amiodarone during reperfusion are supposed to be due to a protection against the deleterious effect of excess matrix calcium on mitochondrial energy metabolism.
Abstract: This study was carried out in order to determine if the efficiency of amiodarone, a class III antiarrhythmic agent, is associated with changes in mitochondrial oxidative phosphorylation. A population of 30 rats were treated with amiodarone (100 mg/kg/day) for 5 days. A second population receiving only vehicle was used as control. The hearts were perfused according to the working mode. After 15 min of normoxic perfusion, the left main coronary artery was ligated and the ligation was maintained for 20 min. The ligation was removed and reperfusion continued for a further 30 min. The electrocardiogram was monitored continuously. At the end of perfusion, the ischemic and non ischemic areas were visually separated and mitochondria were harvested from each area. Their oxidative and energy metabolism were assessed with palmitoylcarnitine as substrate in 2 respiration media differing in their free calcium concentration (0 or 0.34 μm). In normoxic conditions, amiodarone treatment increased the cardiac metabolic efficiency (mechanical work to oxygen consumption ratio). The local ischemia decreased the aortic and coronary flows without modifying the cardiac metabolic efficiency. Amiodarone treatment maintained the aortic flow at a significantly higher value; the duration of severe arrhythmias was significantly decreased by the drug. The reperfusion of the ischemic area allowed the partial recovery of fluid dynamics. The coronary flow was restored to 89% of the pre ischemic value. Conversely, the aortic flow never exceeded that measured at the end of ischemia, partly due to the important development of severe arrhythmias. The recovery of aortic flow and metabolic efficiency during reperfusion was improved by amiodarone treatment; ventricular tachycardia and fibrillation duration were reduced. In the mitochondria issued from the normoxic area, the energy metabolism was not altered by the amiodarone treatment, but the presence of calcium in the respiration medium modified the oxidative phosphorylation. The divalent cation slightly decreased the state III respiration rate and increased noticeably the state IV respiration rate. This was associated with an important mitochondrial AMP production and maintenance of ADP in the respiration medium. This energy wasting was reported to decrease the mitochondrial metabolic efficiency. After an ischemia-reperfusion sequence, mitochondrial oxidation phosphorylation was reduced and amiodarone treatment amplified this decrease. This was presumably due to an increased mitochondrial calcium accumulation. Thus, the beneficial properties of amiodarone during reperfusion are supposed to be due to a protection against the deleterious effect of excess matrix calcium on mitochondrial energy metabolism.
14 citations
TL;DR: The Ca2+- and ADP-Mg-induced uncoupling might be partly responsible for the mechanical abnormalities observed during low-flow ischemia.
Abstract: This study was designed to determine the effect of calcium and ADP-Mg on the oxidative phosphorylation in isolated cardiac mitochondria. The influence of cyclosporin A was also evaluated. The mitochondria were extracted from rat ventricles. Their oxidative phosphorylations were determined in two respiration media with different free Ca2+ concentrations. Respiration was determined with palmitoylcarnitine and either ADP- or ADP-Mg. With elevated free Ca2+concentrations and ADP-Mg, the transition state III to state IV respiration did not occurred. The ADP:O ratio was reduced. The phenomenon was not observed in the other experimental conditions (low free Ca2+ concentration with either ADP- or ADP-Mg or elevated free Ca2+ concentration with ADP-). Uncoupling was allied with a constant AMP production, which maintained an elevated ADP level in the respiration medium and prevented the return to state IV respiration. It was also observed in a respiration medium devoid of free Ca2+ when the mitochondria were pre-loaded with Ca2+. Uncoupling was inhibited by cyclosporin A. Furthermore, the Krebs cycle intermediates released from14C-palmitoylcarnitine oxidation revealed that succinate was increased by elevated free Ca2+ and ADP-Mg. Succinate is a FAD-linked substrate with low respiration efficiency. Its accumulation could account for the decreased ADP:O ratio. The Ca2+- and ADP-Mg-induced uncoupling might be partly responsible for the mechanical abnormalities observed during low-flow ischemia. (Mol Cell Biochem 000: 000-000, 1999)
12 citations
TL;DR: Bupivacaine significantly lowered the increase in extracellular potassium in a dose-related fashion and the association with flumazenil blunted the effects of bupivacain, proving effective in protecting erythrocytes against oxidative stress.
Abstract: Aims To examine the effects of bupivacaine on erythrocytes submitted to an oxidative stress (AAPH) and to provide evidence for an in vitro interaction between bupivacaine and flumazenil
Methods Human erythrocytes were studied with or without AAPH in the presence of different concentrations of bupivacaine (015, 03, 09 and 18 mmol l−1 ), or flumazenil (016 mmol l−1 ) and with the association of flumazenil and two doses of bupivacaine (015 and 03 mmol l−1 ) Potassium efflux was measured by flame photometry at t0, and every 30 min for 2 h
Results In the absence of AAPH, extracellular potassium remained unchanged Oxidative stress induced a significant increase in extracellular potassium, which was not modified by incubation with flumazenil Bupivacaine significantly lowered the increase in extracellular potassium in a dose-related fashion The association with flumazenil blunted the effects of bupivacaine
Discussion In this model, bupivacaine proved effective in protecting erythrocytes against oxidative stress Flumazenil interacted with bupivacaine and blunted its protective effects
7 citations