Persistent subclinical renal injury in female rats following renal ischemia-reperfusion injury

The incidence of acute kidney injury (AKI) continues to rise in both men and women. Although creatinine levels return to normal quicker in females following AKI than in males, it remains unclear whether subclinical renal injury persists in young females post-AKI. This study tested the hypothesis that AKI results in subclinical renal injury in females despite plasma creatinine returning to sham levels. For the present study, 12-13-week-old female Sprague-Dawley (SD) rats were randomized to sham or 45-minute warm bilateral ischemia-reperfusion surgery as an experimental model of ischemic AKI. Rats were euthanized 1, 3, 7, 14, or 30 days post-AKI/sham. Plasma creatinine, cystatin C, kidney injury molecule 1 (KIM-1), and NGAL were quantified via assay kits or immunoblotting. Kidneys were processed for histological analysis to assess tubular injury and fibrosis, and for electron microscopy to examine mitochondrial morphology. Immunoblots on kidney homogenates were performed to determine oxidative stress and apoptosis. Plasma creatinine levels were increased 24 hours post-AKI but returned to sham control levels three days post-AKI. However, cystatin C, KIM-1, and NGAL were increased 30 days post-AKI compared with sham. Tubular injury, tubulointerstitial fibrosis, and mitochondrial dysfunction were all increased in 30-day post-AKI rats compared with sham. Additionally, 30-day post-AKI rats had higher p-JNK expression and lower antioxidant enzyme glutathione peroxidase and catalase levels compared with sham. AKI resulted in higher expression of cleaved caspase 3, TUNEL+ cells, and caspase 9 than sham. Despite the normalization of creatinine levels, our data support the hypothesis that subclinical renal injury persists following ischemia-reperfusion injury in young female rats.