In vivo visualization of albumin degradation in the proximal tubule

Abstract

Albuminuria is a key marker of renal injury and a major risk factor for cardiovascular disease. In vivo imaging techniques with fluorescent albumin have allowed visualization of its movement within the whole kidney but they could not distinguish between intact and degraded albumin. To visualize albumin degradation in proximal tubular cells in vivo we used an albumin conjugate (dye quenched (DQ)-albumin), which only fluoresces when it is degraded. In cultured proximal tubule cells, the fluorescent signal from DQ-albumin was dependent on endocytosis and lysosomal function and showed that at any time about 40% of endocytosed DQ-albumin was degraded. Significant accumulation of conventional Texa..