Langendorff Heart Perfusion

To investigate tracer response to decreased mitochondrial membrane potential, uptake and kinetic modeling of ¹⁸F-MitoPhos was compared with that of the SPECT lipophilic cardiac tracer ^99mTc-sestamibi in male Wistar rat hearts (n = 4–6 per group, 300–330 g) on a triple-γ-detection Langendorff perfusion setup, previously described (22,23). Tracers were compared under normoxic control perfusion and in hearts treated with the mitochondrial membrane potential uncoupler carbonyl cyanide 3-chlorophenylhydrazone (CCCP).

After intraperitoneal injection of pentobarbital, hearts were excised from male Wistar rats and cannulated onto a Langendorff perfusion rig. Hearts were perfused with modified Krebs–Henseleit buffer (37°C gassed with 95% O₂/5% CO₂) at a constant flow rate of 14 mL/min. Cardiac tracer retention and washout were monitored throughout each experiment using GinaSTAR software (Raytest Ltd, UK) via the triple-γ-detection system, whereas cardiac contractile function was monitored with an intraventricular balloon connected to a Powerlab system (AD Instruments Ltd) running Labchart software (AD Instruments Ltd). After a stabilization period of 20 min, CCCP (at a final concentration of 300 nmol/L) or vehicle was infused into the aortic cannula via a side arm. After 25 min, a bolus of radiotracer (∼1 MBq, 50–100 μL) was injected into the arterial line. Cardiac radiotracer uptake was recorded and decay-corrected, and the exponential washout component was calculated from least-squares fit of data from 2 min after injection.