Plasma concentrations of most electrolytes did not change during I R with the e ception of low potassium that decreased after 25 minutes of cooling whereas it increased significantly after 60 minutes of reperfusion. CRP levels were constant between healthy animals and T1. During CPB however, CRP levels decreased significantly at T2 and T5, possibly due to the ini tial priming of the system with HAES. CK MB levels were decreased after cooling but increased after reperfusion if compared to levels of healthy animals and T1. Plasma lactate levels showed a slight increase after cooling but an e plicit increase after 60 minutes of reperfusion as shown in Table 2. Other clinical biochemistry parameters are listed in Additional file 2 Table S1 of the supplementary data.

Increase in IL 6 and TNF plasma levels after reperfusion Increased levels of the pro inflammatory cytokines TNF and IL 6 can be observed during CPB. IL 6 increase is associated with reperfusion and in duces a variety of downstream events, e. g. cardioprotec tion by JAK STAT signalling during CPB. We therefore determined the plasma IL 6 and TNF levels at T1, T2 and T5. Rewarming and reperfusion following DHCA led to a dramatic increase of IL 6 in all ani mals, causing significantly elevated values as compared to time points prior to DHCA or as compared to values observed in healthy animals. Note worthy, IL 6 levels of the T1 and T2 samples all lay under the detection level. TNF levels were also significantly elevated after reperfusion as compared to prior time points and to healthy animals.

In contrast to the IL 6 levels, TNF levels were already elevated after 25 minutes of cooling. Therewith the present study could demon strate that I R injury as applied in the presented model leads to an increase of the pro inflammatory cytokines IL 6 and TNF. I R induced alterations in e pression and phosphorylation status of intracellular signal mediators and heat shock proteins Key intracellular players of the I R related signal trans duction were evaluated to further e plore the validity of the presented model as a tool for scientific work on I R. I R modulates the kinases ERK1 2, p38 and JNK by al tering their site specific phosphorylation. Consequently, we analysed changes in phosphorylation of ERK1 2 at Y202 T204, of p38 at T180 182 and of JNK at T183 Y185 after hypothermic global ischaemia and normothermic re perfusion. Furthermore, the e pression of the heat shock proteins HSP 70 and HO 1, which are induced immedi ately after ischaemia as organ protective mechanisms, was analysed. As a mediator of cellular inflammatory response, phosphorylation of the transcription GSK-3 factor STAT3 at Y705, which among others is induced by IL 6, was assessed.