BackgroundIn patients with acute myocardial infarction, the one‐year mortality remains at 7‐15% despite successful interventional reperfusion. Thus, innovative treatment strategies beyond reperfusion are needed. In isolated perfused rat hearts, triiodothyronine (T3), when given during early reperfusion in a supraphysiological concentration, improves left ventricular function and reduces infarct size (Basic Res Cardiol 2021;116:27).AimTo investigate whether or not such acute, non‐genomic effects of T3 also protect human myocardium.MethodsWe isolated right atrial trabeculae from patients undergoing routine coronary artery bypass grafting and investigated the effect of T3 on contractile function during hypoxia/reoxygenation. Trabeculae (≥ 3 mm length, ≤ 1 mm diameter) were isolated in cardioplegic buffer and transferred to Tyrode buffer. Electrically initiated (1 Hz) developed force of contraction (mN/mm2) was recorded for 10 min at baseline (95% O2 – 5% CO2, glucose). Hypoxia/reoxygenation (60 min/30 min) was induced by changing the buffer gas supply and composition and by increasing the stimulation rate (95% N2 – 5% CO2, choline chloride, 3 Hz) and returning back to baseline. T3 (500 µg/l) or NaOH (as solvent control), respectively, was administered A) during hypoxia and reoxygenation (n=11 vs. n=10) or B) 15 min before and during reoxygenation (n=12 vs. n=14).ResultsAt baseline, before T3 or NaOH treatment, the contractile function of trabeculae was comparable (mN/mm2: 15.4±3.5, 13.8±4.4 in protocol A, and 14.5±4.1, 13.7±4.0 in protocol B, respectively). T3 improved the contractile function during reoxygenation, irrespectively of whether given continuously (A) or just before and during reoxygenation (B; see Figure).ConclusionT3 protects patient myocardium: contractile function is improved during reoxygenation in right atrial trabeculae. This bioassay will now permit an identification of causally involved cardioprotective signaling molecules of such non‐genomic protection in human tissue by T3.
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