Metabolic acidosis aggravates experimental acute kidney injury

Ischemia/reperfusion (I/R) injury and metabolic acidosis (MA) are two critical conditions that may simultaneously occur in clinical practice. The result of this combination can be harmful to the kidneys, but this issue has not been thoroughly investigated. The present study evaluated the influence of low systemic pH on various parameters of kidney function in rats that were subjected to an experimental model of renal I/R injury. Metabolic acidosis was induced in male Wistar rats by ingesting ammonium chloride (NH4Cl) in tap water, beginning 2days before ischemic insult and maintained during the entire study. Ischemia/reperfusion was induced by clamping both renal arteries for 45min, followed by 48h of reperfusion. Four groups were studied: control (subjected to sham surgery, n=8), I/R (n=8), metabolic acidosis (MA; 0.28M NH4Cl solution and sham surgery, n=6), and MA+I/R (0.28M NH4Cl solution plus I/R, n=9). Compared with I/R rats, MA+I/R rats exhibited higher mortality (50 vs. 11%, p=0.03), significant reductions of blood pH, plasma bicarbonate (pBic), and standard base excess (SBE), with a severe decline in the glomerular filtration rate and tubular function. Microscopic tubular injury signals were detected. Immunofluorescence revealed that the combination of MA and I/R markedly increased nuclear factor κB (NF-κB) and heme-oxygenase 1 (HO-1), but it did not interfere with the decrease in endothelial nitric oxide synthase (eNOS) expression that was caused by I/R injury. Acute ischemic kidney injury is exacerbated by acidic conditions.