Cloricromene reduces myocardial infarct size in rabbits when administered during the early reperfusion period

A modified rabbit model of reperfused myocardial infarction for cardiac MR imaging research

We sought to obtain a rabbit myocardial infarction (MI) model for research with cardiac magnetic resonance imaging (cMRI) by overcoming a few technical difficulties. A novel endotracheal method was developed for intubation and ventilation. Fourteen rabbits were divided into group-1 (n = 8) with open-chest occlusion of left circumflex coronary artery and closed-chest reperfusion, and group-2 (n = 6) of non-ischemic control; and received ECG-triggered cMRI with delayed contrast enhancement (DE-cMRI) at a 1.5 T clinical scanner. The MI areas in group-1 were morphometrically compared between DE-cMRI and histochemically stained specimens. Left ventricular (LV) functions were compared between two groups.The success rate of intubation and reperfused MI was 8/8 and 6/8, respectively. Global and regional LV functions significantly decreased in group-1 as evidenced by significant hypokinesis of lateral LV-wall and wall thickening (P \ 0.001). Mean MI-area was 19.41 +/- 21.92% on DE-cMRI and 19.10 +/- 22.61% with histochemical staining (r = 0.985). Global MI-volume was 17.92 +/- 7.42% on DE-cMRI and 16.62 +/- 7.16% with histochemistry (r = 0.994). The usefulness of this model was successfully tested for assessing a new contrast agent. The present rabbit MI model may offer a practical platform for more translational research using clinical MRI-facilities.

Cloricromene reduces infarct size and alters postischaemic blood flow defects in dog myocardium

1. The aim of the present investigation was to evaluate the effect of cloricromene on myocardial infarct size, regional myocardial blood flow and neutrophil accumulation in a canine model of ischaemia-reperfusion. 2. Dogs were instrumented to measure blood pressure, left anterior descending (LAD) coronary flow (flow probe) and regional myocardial blood flow (coloured microspheres). Two groups were studied: (i) CLO (n = 8) received an infusion of cloricromene (15 micrograms/kg per min); and (ii) VEH (n = 8) received saline. Infusions began at the onset of ischaemia (60 min) and continued through reperfusion (180 min). 3. Haemodynamic responses were not different between groups. Cloricromene reduced the area of necrosis expressed as a percentage of the area at risk from 35 +/- 3% in the VEH group to 23 +/- 4% in the CLO group (P < 0.05). Regional myocardial blood flow in the ischaemic region was different between groups; VEH dogs showed an early reperfusion hyperaemia followed by a progressive reduction in flow, while CLO dogs exhibited a gradual increase in reflow in the absence of an early hyperaemic response (P < 0.05). Left anterior descending flow was enhanced during the reperfusion period in the CLO group compared with VEH (P < 0.05). Cloricromene reduced polymorphonuclear neutrophil (PMN) infiltration (myeloperuxidase activity) in all myocardial regions when compared with VEH (non-ischaemic zone, 0.34 +/- 0.54 vs 0.05 +/- 0.01 IU/100 mg; ischaemic zone, 2.03 +/- 0.80 vs 0.24 +/- 0.08 IU/100 mg; and necrotic zone, 0.56 +/- 0.04 vs 3.59 +/- 1.09 IU/100 mg for VEH vs CLO groups, respectively; P < 0.01). In a separate in vitro preparation, cloricromene reduced adherence of platelet-activating factor (PAF)-stimulated PMN to canine coronary endothelium. Stimulation of PMN by 100 nmol/L PAF resulted in adherence of 176 +/- 36 compared with 48 +/- 12 cells/mm2 in PAF-stimulated PMN treated with 100 mumol cloricromene (P < 0.001). 4. These data indicate that cloricromene reduces myocardial infarct size in a canine model of ischaemia-reperfusion injury. Postischaemic blood flow patterns are significantly different in cloricromene-treated dogs. Cloricromene-mediated reductions in infarct size, neutrophil accumulation and adherence may play a role in this effect.