doi: 10.1093/ndt/gfr222 Original Article Albuminuria increases cystatin C excretion: implications for urinary biomarkers

Background. Low-molecular weight (LMW) proteins, in-cluding albumin and novel urinary biomarkers of acute kidney injury (AKI) such as cystatin C and neutrophil ge-latinase-associated lipocalin (NGAL), are normally ab-sorbed from the glomerular filtrate by receptor-mediated transport. We evaluated the effect of albuminuria on urinary excretion of novel biomarkers. Methods. Sprague–Dawley rats given four injections over 2 days of 5 mg/g body wt/day bovine serum albumin (BSA) in saline were compared with controls given saline alone. Uri-nary cystatin C, albumin and protein excretion rates were compared prior to treatment (Day 1), after treatment (Day 2) and 4 days later (Day 6). A preliminary assessment of the clinical effect of proteinuria on the filtered urinary biomarker