Changes in proton transverse relaxation times of rat myocardium that has suffered a previous oxidative insult

An oxidative insult can induce severe damage, as in the phenomenon of myocardial ischemia and reperfusion. However, there are situations in which the damage is not so obvious (e.g., silent ischemia or aging), and the negative effects will be seen only in time. Our aim was to reveal these small changes in the myofilaments by using the nuclear magnetic resonance (NMR) technique. We used Wistar rat hearts in a constant-pressure Langendorff system, perfused with oxygenated Krebs-Henseleit buffer at 37°C. After 15 minutes of stabilization, the hearts were perfused with buffer supplemented with H₂O₂ at 50, 75, or 100 μmol/L for 15 or 30 minutes. Fifteen-minute and 45-minute perfusion controls and unperfused hearts were also collected. Heart rate (HR) and left ventricular developed pressure (LVDP) were determined with the help of a latex balloon, inserted in the left ventricle and connected with a pressure transducer. Proton transverse relaxation times (T ₂) were determined at the end of the experiment.T ₂ values were measured again in the same tissue fragments after they had been glycerinated and incubated in relaxation and rigor media. The functional parameters (HR, LVDP, coronary flow) were not significantly changed in control and 50 μmol/L H₂O₂ groups but were increased in the 75 μmol/L H₂O₂ group and significantly decreased in the 100 μmol/L H₂O₂ group.T ₂ is significantly decreased in rigor media starting with 50 μmol/L H₂O₂ administrated for 30 minutes and does not correlate with dose and duration of the oxidative insult.T ₂ in rigor is shorter than in relaxation media within the groups, and this difference is increased in the treated hearts.