Optimal pH for simple cold storage or machine perfusion of dog kidneys with UW solution

Metabolic suppression by temperature is a key to successful organ preservation. Additional methods for inducing metabolic suppression may further improve organ preservation. Extracellular acidosis has been shown to suppress warm anoxic injury to various isolated cells. Acidosis may suppress enzymes with a pH optimum at the pH of the cytosol (pH 7.3). In this study, the combination of hypothermia and acidosis was used to determine if it would improve renal preservation. Dog kidneys were cold-stored (CS) for 48 h in University of Wisconsin (UW) solution with the pH adjusted to 6.4, 6.8, 7.4, or 7.8. Kidneys were also machine-perfused (MP) for 3 days with the gluconate perfusion solution (Belzer's machine perfusion solution, MPS) at pHs similar to those tested for CS. Renal function (serum creatinine, SCr) and survival were recorded in immediate contralateral nephrectomized recipients. On the basis of maximum SCr values, kidneys preserved by CS or MP were best preserved at pHs of 7.4 or 7.8. At a pH of 6.8, SCr values were elevated and returned to normal at a slower rate than in those preserved at higher pHs. This study shows that acidosis is not cytoprotective to cold-stored dog kidneys and causes preservation/reperfusion injury.