Rat model of myocardial infarction

Male Sprague–Dawley rats (weight 250 to 300 g) were acclimatized for a period of 1 week prior to the start of the experimental protocol. After the acclimatization period, the rats were divided in a random manner into vehicle controls (2 groups, n = 16 each) and 10 mM SCN^– treated groups (2 groups, n = 16 each), with the SCN⁻ (as NaSCN) dissolved in drinking water, for 1 week of preconditioning prior to surgery. This dosing period has been previously shown to result in significant and sustained elevations in plasma SCN⁻ concentrations^25,26. Both food and water were available ad libitum. All procedures were approved by the Royal North Shore Hospital Animal Care and Ethics Committee (approval no. 5405-005A) and the study was carried out in compliance with the ARRIVE guidelines. Myocardial IR was induced as described previously, using an open‐chest method⁶. Ischemia was induced for 30 min by transient suture ligation of the left anterior coronary artery approximately 2 to 3 mm distal to the junction of pulmonary artery and left atrial appendage. Sham operated animals underwent the same surgical procedure and ligation placement, but the ligature was not tightened in these animals. For the IR animals, the ligature was released after the 30 min period. For each group, the rats were then allowed to recover for either 24 h or 4 weeks before sacrifice. Immediately prior to sacrifice, rats destined for MRI analysis (n = 8 per group with 24 h recovery period) had the LAD ligature retightened. The MRI contrast agent gadobenate dimeglumine (Multihance, 0.5 M, 0.4 mL kg⁻¹) was infused via a tail vein cannula 10 min before sacrifice, and 2 min before sacrifice, iron microparticles (Dynabeads MyOne tosylactivated; 4.5 mg kg⁻¹) were also infused via the tail vein cannula as described previously⁸⁶. These agents modulate the T1 (gadolinium) or T2/T2* (iron oxide) relaxation of adjacent water protons. The remaining animals that were not infused with contrast agents had blood samples collected for analysis, including SCN⁻ concentrations, biomarkers of HF, as well as metabolomic analyses. The overall experimental protocol is indicated in Fig. 1. All methods were performed in accordance with the relevant guidelines and regulations.