The effect of a low molecular weight inhibitor of lipid peroxidation on ultrastructural alterations to ischemia-reperfusion in the isolated rat heart

The effects of H290/51, a novel indenoindole derivative inhibitor of lipid peroxidation, on ultrastructural changes during cardiac ischemia-reperfusion injury were investigated. Langendorff-perfused rat hearts were exposed to 30 minutes of global ischemia followed by 20 minutes of reperfusion: Group A: Control hearts with standard buffer perfusion with vehicle added. Group B: H290/51 (10-6 mol/l) added to buffer throughout stabilisation and reperfusion. In an additional Group C, where hearts were given H290/51, but not subjected to ischemia, the ultrastructure was preserved till the end of reperfusion. Absolute volumes and calculated volume fractions (Vv) of tissue and subcellular components were assessed with quantitative stereologic morphometry. After ischemia the increase in volume of extracellular interstitium was inhibited by H290/51 (247±80 vs. 159±50ml, mean±SD, groups A and B, respectively, p<0.05). The Vv (interstitium/myocard) was higher in control hearts (0.318±0.062 vs. 0.206±0.067, p<0.05). Vv (cell edema/myocyte) was higher in the control group (0.144±0.07 vs. 0.083±0.033, p<0.05). Vv (myocyte/myocard) was higher in group B after ischemia than in the control group (0.622±0.071 vs. 0.707±0.052, p<0.05). The decreased Vv (capillary/myocard) after ischemia was inhibited by H290/51. After reperfusion there was no difference between groups. Treatment with H290/51 reduced edema and ensured better preserved sarcolemmal membrane structure during ischemia. The effect was no longer present after reperfusion.

Myocardial protection by co-administration of l-arginine and tetrahydrobiopterin during ischemia and reperfusion

Background Reduced bioavailability of nitric oxide (NO) is a key factor contributing to myocardial ischemia and reperfusion injury. The mechanism behind the reduction of NO is related to deficiency of the NO synthase (NOS) substrate l-arginine and cofactor tetrahydrobiopterin (BH4) resulting in NOS uncoupling. The aim of the study was to investigate if the combination of l-arginine and BH4 given iv or intracoronary before reperfusion protects from reperfusion injury. Methods Sprague-Dawley rats and pigs were subjected to myocardial ischemia and reperfusion. Rats received vehicle, l-arginine, BH4, l-arginine + BH4 with or without the NOS-inhibitor L-NMMA iv 5 min before reperfusion. Pigs received infusion of vehicle, l-arginine, BH4 or l-arginine + BH4 into the left main coronary artery for 30 min starting 10 min before reperfusion. Results Infarct size was significantly smaller in the rats (50 ± 2%) and pigs (54 ± 5%) given l-arginine + BH4 in comparison with the vehicle groups (rats 65 ± 3% and pigs 86 ± 5%, P &lt; 0.05). Neither l-arginine nor BH4 alone significantly reduced infarct size. Administration of L-NMMA abrogated the cardioprotective effect of l-arginine + BH4. Myocardial BH4 levels were 3.5- to 5-fold higher in pigs given l-arginine + BH4 and BH4 alone. The generation of superoxide in the ischemic-reperfused myocardium was reduced in pigs treated with intracoronary l-arginine + BH4 versus the vehicle group (P &lt; 0.05). Conclusion Administration of l-arginine + BH4 before reperfusion protects the heart from ischemia-reperfusion injury. The cardioprotective effect is mediated via NOS-dependent pathway resulting in diminished superoxide generation. © 2013 Elsevier Ireland Ltd

Myocardial protection by co-administration of l-arginine and tetrahydrobiopterin during ischemia and reperfusion

Background Reduced bioavailability of nitric oxide (NO) is a key factor contributing to myocardial ischemia and reperfusion injury. The mechanism behind the reduction of NO is related to deficiency of the NO synthase (NOS) substrate l-arginine and cofactor tetrahydrobiopterin (BH4) resulting in NOS uncoupling. The aim of the study was to investigate if the combination of l-arginine and BH4 given iv or intracoronary before reperfusion protects from reperfusion injury. Methods Sprague-Dawley rats and pigs were subjected to myocardial ischemia and reperfusion. Rats received vehicle, l-arginine, BH4, l-arginine + BH4 with or without the NOS-inhibitor L-NMMA iv 5 min before reperfusion. Pigs received infusion of vehicle, l-arginine, BH4 or l-arginine + BH4 into the left main coronary artery for 30 min starting 10 min before reperfusion. Results Infarct size was significantly smaller in the rats (50 ± 2%) and pigs (54 ± 5%) given l-arginine + BH4 in comparison with the vehicle groups (rats 65 ± 3% and pigs 86 ± 5%, P < 0.05). Neither l-arginine nor BH4 alone significantly reduced infarct size. Administration of L-NMMA abrogated the cardioprotective effect of l-arginine + BH4. Myocardial BH4 levels were 3.5- to 5-fold higher in pigs given l-arginine + BH4 and BH4 alone. The generation of superoxide in the ischemic-reperfused myocardium was reduced in pigs treated with intracoronary l-arginine + BH4 versus the vehicle group (P < 0.05). Conclusion Administration of l-arginine + BH4 before reperfusion protects the heart from ischemia-reperfusion injury. The cardioprotective effect is mediated via NOS-dependent pathway resulting in diminished superoxide generation. © 2013 Elsevier Ireland Ltd

Expression of arginase II in the cytosolic and mitochondrial fractions of a representative myocardial sample.

<p>For comparison the expression of the mitochondrial membrane protein cytochrome oxidase (COX) is depicted.</p

Area at risk (A), infarct size (B) and representative triphenyltetrazolium chloride stained cross section of the left ventricle (C) of the groups given ic vehicle, the arginase inhibitor nor-NOHA, the combination of the NOS-inhibitor L-NMMA and nor-NOHA, or iv administration of nor-NOHA.

<p>Mean and SEM; n = 5–7. Significant difference from the vehicle group is indicated; **P<0.01.</p

Experimental protocols.

<p>The animals were subjected to 40 min of ischemia and 240 min reperfusion. The groups were randomized to vehicle ic, nor-NOHA ic, nor-NOHA combined with L-NMMA ic or nor-NOHA iv. All infusions were started at 30 min of ischemia except L-NMMA which was started at 25 min of ischemia. The infusions were maintained until 5 min of reperfusion.</p