Background/Aims: The anti-apoptotic effect of an increase in the extracellular concentration of potassium ([K⁺]) has been confirmed in vitro. However, it is not yet known whether elevated serum [K⁺] exerts a cerebroprotective effect in vivo. In this study, we aimed to explore the effect of elevated serum [K⁺] in a rat model of middle cerebral artery occlusion and reperfusion (MCAO/R). Methods: Rats subjected to 90-min MCAO received 2.5% KCL, 1.25% KCL, or a normal saline solution at a dose of 3.2 mL/kg at the onset of reperfusion. Rats that were subjected to vascular exposure and ligation without MCAO were defined as the Sham group. Serum [K⁺] was determined using a blood gas analyzer at 1 min after medicine administration. At 24 h post-reperfusion, rat brains were harvested and processed for 2% 2,3,5-triphenyltetrazolium chloride staining, terminal deoxynucleotidyl transferase-mediated 2′-deoxyuridine 5′-triphosphate-biotin nick end labeling staining, detection of caspase-3 and cleaved-caspase-3 by western blotting, detection of reactive oxygen species (ROS) by dihydroethidium staining, and observation of mitochondrial structure by electron microscopy. In addition, malondialdehyde (MDA), adenosine triphosphate (ATP), total superoxide dismutase (T-SOD), cytochrome C oxidase (COX) activity, and mitochondrial permeability transition pore (MPTP) opening were measured using detection kits. Results: The results showed that elevated serum [K⁺] decreased cerebral injury and apoptosis, reduced ROS and MDA levels and MPTP opening, increased ATP levels and cytochrome C oxidase activity, and improved mitochondrial ultrastructural changes, although there was no significant difference in T-SOD activity. Conclusion: These findings suggested that elevated serum [K⁺] could alleviate cerebral ischemia-reperfusion injury and the mechanism may be associated with the preservation of mitochondrial function.

Background Various and opposite roles of epigallocatechin gallate (EGCG) have been reported in different studies. We aimed to investigate how EGCG affects the cerebral injury in a cardiac arrest/cardiopulmonary resuscitation (CA/CPR) model of rat. Methods The rats which were subjected to CA/CPR randomly received low dose of EGCG (3 mg/kg, Low-EGCG group, n=16), high dose of EGCG (9 mg/kg, High-EGCG group, n=16) and equal volume of 0.9% saline solution (NS group, n=16) at the first minute after return of spontaneous circulation (ROSC). The rats underwent anesthesia and intubation were defined as Sham group (n=16). Twenty-four hours after ROSC, neural defect score (NDS), ROS fluorescence intensity, degree of mitochondrial permeability transition pore (mPTP) opening, ATP contents and mitochondrial ATP synthase expression were evaluated in the four groups. The expression of extracellular signal-regulated kinase (ERK) activity and cleaved-caspase 3 were also detected by Western blot. Results CA/CPR induced severe ischemia-reperfusion injury (IRI), resulted in mitochondrial dysfunction and upregulated phosphorylation of ERK. EGCG dose-dependently alleviated the IRI after CA/CPR, inhibited ERK activity and restored mitochondrial function and, as indicated by improved NDS, reduced ROS level, decreased mPTP opening, elevated ATP content, increased ATPase expression and downregulated cleaved-caspase 3 level. Conclusion EGCG alleviated global cerebral IRI by restoring mitochondrial dysfunction and ERK modulation in a rat CA/CPR model, which might make it a potential candidate agent against IRI after CA/CPR in the future. Further study is needed to determine whether higher dosage of EGCG might aggravate cerebral IRI post-CA/CPR.