Evaluation of Normothermic Ischemia and Simple Cold Preservation Injury in Pig Kidney by Proton Nuclear Magnetic Resonance Spectroscopy

The isolated perfused pig kidney (IPK) model was used to mimick the non-heart-beating donor situation. This model was performed to assess initial renal functions after normothermic ischemia, cold flush, and 24 hr cold-storage preservation (CSP) with Euro-Collins and to determine normothermic ischemia and reperfusion impairment by biochemical, histological, and proton nuclear magnetic resonance (NMR) spectroscopy analysis. Twenty-four pig kidneys were used. There were three experimental groups: Group 1 (G1), control kidneys flushed with cold heparinized saline and immediately perfused; Group 2 (G2), cold flush followed by 24 hr CSP and reperfusion; and Group 3 (G3), 30 min of normothermic ischemia followed by cold flush and 24 hr CSP and reperfusion. Kidneys were perfused for 2 hr at 37.5°C for functional evaluation. Perfusate flow rate is significantly different for G3 (P< 0.01). Glomerular filtration rate is less in G3 (P< 0.05). Fractional reabsorptions of sodium (FRNa+) and glucose (Glc) excretion in urine are different in G3 (P< 0.01 andP< 0.05, respectively). Amino acid excretion in NMR spectroscopy was higher in G3 (P< 0.05). Elevated levels of trimethylamine-N-oxide (TMAO) and lactate (Lac) were detected by proton NMR spectroscopy in G2 and particularly G3. A peak is present in G3 and related with poor glomerular and tubular functions and worse histological data. Malondialdehyde tissue level was higher in G3. This study shows that the IPK with proton NMR spectroscopy may be a useful method in the evaluation of kidneys after cold ischemia and transplantation. This model might be suitable for a variety of experimental protocols, particularly to improve functional performance after ischemia and reperfusion.