The co-application of hypoxic preconditioning and postconditioning abolishes their own protective effect on systolic function in human myocardium

Abstrakt

Background: Ischemic preconditioning (IPC) and postconditioning (POC) are well documented to trigger cardioprotection against ischemia/reperfusion (I/R) injury, but the effect of their both co-application remains unclear in human heart. The present study sought to assess the co-application of IPC and POC on fragments of human myocardium in vitro.

Methods: Muscular trabeculae of the human right atrial were electrically driven in the organ bath and subjected to simulated I/R injury – hypoxia/re-oxygenation injury in vitro. To achieve IPC of trabeculae the single brief hypoxia period preceded the applied lethal hypoxia, and to achieve POC triple brief hypoxia periods followed the lethal hypoxia. Additional muscular trabeculae were exposed only to the hypoxic stimulation (Control) or were subjected to the non-hypoxic stimulation (Sham). 10 μM norepinephrine (NE) application ended every experiment to assess viability of trabeculae. The contraction force of the myocardium assessed as a maximal amplitude of systolic peak (%Amax) was obtained during the whole experiment’s period.

Results: Co-application of IPC and POC resulted in decrease in %Amax during the re-oxygentaion period and after NE application, as compared to Control (30.35 ± 2.25 vs. 41.89 ± 2.25, 56.26 ± 7.73 vs. 65.98 ± 5.39, respectively). This was in contrary to the effects observed when IPC and POC were applied separately.

Conclusions: The co-application of IPC and POC abolishes the cardioprotection of either intervention alone against simulated I/R injury in fragments of the human right heart atria.