Renal cortical antioxidant enzymes are not inactivated by cardiac arrest-resuscitation in pigs

Abstract

Purpose: Cardiac arrest interrupts renal blood flow, and cardiopulmonary resuscitation (CPR) and restoration of sinus rhythm and renal perfusion may generate reactive oxygen species (ROS) that damage the kidneys. Cardiac arrest, CPR and cardioversion inactivate ROS-sensitive enzymes in heart and brain, but intravenous sodium pyruvate (PYR) treatment preserves the enzymes and prevents heart and brain injury. The impacts of cardiac arrest-CPR and PYR on ROS-sensitive antioxidant enzymes in renal cortex is unknown. This study tested the hypothesis that cardiac arrest-CPR-recovery inactivates, while PYR preserves, these renal enzymes. Methods: Yorkshire swine (c. 30 kg) were intubated and mechanically ventilated with 1-3% isoflurane in O2. Cardiac electrical activity was monitored by lead II electrocardiography. Cardiac pacing (60 Hz) produced ventricular fibrillation, and ventilation was suspended. From 6 to 10 min cardiac arrest, precordial chest compressions were applied (100/min), and then transthoracic DC countershocks were administered to achieve cardioversion, and ventilation resumed. PYR (n=7) or NaCl (n=6) were infused iv (0.1 mmol/kg/min) from 5.5 min cardiac arrest to 60 min recovery. Non-arrested sham pigs (n=9) also were studied. At 4 h recovery, the kidneys were excised, and renal cortex biopsied and snap-frozen in liquid N2. The biopsies were pulverized and extracted in 1 mM phosphate buffer (pH 7.2). Extract activities of glutathione peroxidase (GP), glutathione reductase (GR), the anti-glycation enzyme glyoxylase-1 (GLO-1), and NADPH-generating glucose 6-phosphate dehydrogenase (G6PD) and isocitrate dehydrogenase (ICD) were assayed at 37°C by spectrophotometry and normalized to total protein. Results: Contrary to our hypothesis, neither cardiac arrest-CPR-recovery, nor PYR treatment, produced statistically significant effects (single-factor ANOVA; a=0.05) on the enzyme activities (U/mg protein: mean±SEM): GP: sham 0.18±0.03, NaCl 0.25±0.07, PYR 0.15±0.02; GR: sham 0.21±0.04, NaCl 0.22±0.05, PYR 0.17±0.01, GLO-1: sham 4.45±0.40, NaCl 4.35±0.86, PYR 3.77±0.80, G6PD: sham 0.62±0.06, NaCl 0.69±0.14, PYR 0.52±0.13; ICD: sham 0.89±0.15, NaCl 1.15±0.28, PYR 0.99±0.12). Conclusions:Ischemic and oxidative stress produced by 10 min cardiac arrest with 4 min CPR did not inflict sufficient ischemic and oxidative stress to inactivate the renal cortex’s antioxidant enzymes, leaving no deficits correctable by PYR treatment.