['Recent evidences indicated that hydrogen (H2) can attenuate organ transplantation induced cold ischemia/reperfusion (I/R) injury if administrated perioperatively. In this study we evaluated whether administrating H2 during the prolonged cold ischemia stage by adding it to Histidine-Tryptophan-Ketoglutarate (HTK) solution fortifies preservation for cardiac grafts.', 'One hundred and twenty-eight Sprague-Dawley (SD) rats were equally randomized to four groups: three H2-rich HTK-treated groups with H2 of different concentrations and traditional HTK-treated group as the control group. Isolated hearts were mounted on the Langendorff apparatus for aerobic perfusion. Following baseline hemodynamic measurements, grafts were arrested and stored in HTK with or without H2 for 6h at 4°C. After this prolonged cold storage, grafts were reperfused and concerned parameters were examined.', "Compared with the control group, preservation in H2-rich HTK significantly enhanced the percentage recovery of hemodynamic parameters, which was parallel to the diminished re-beating time and improved microscopic morphology of myocardium. Oxidative stress associated parameters including 8-hydroxy-2'-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) were decreased while myocardial superoxide dismutase (SOD) activity was preserved. Concentrations of inflammatory mediators including tumor necrosis factor-alpha (TNF-α) and Interleukin-6 (IL-6), percentage of TUNEL-positive cells, expression of pro-apoptotic molecule Bax, and caspase-3 activity were reduced while Bcl-2 mRNA and protein levels were up-regulated in H2-rich HTK groups. The protective effects of H2 were concentration dependent."] Does hydrogen as additive of HTK solution fortify myocardial preservation in grafts with prolonged cold ischemia?