In Vivo Assessment of Individual and Total Proteinuria in Zebrafish Larvae Using the Solvatochromic Compound ZMB741

The robustness of blood filtration in the kidney is supported by two major functions: the molecular sieve of the glomerulus and reabsorption of the proximal tubules. Detecting glomerular dysfunction is challenging because of the compensatory nature of proximal tubule reabsorption. To facilitate pathophysiological studies of the vertebrate kidney, zebrafish pronephroi are used, owing to their simple glomerular and proximal tubular configuration. In this study, a solvatochromic dye with an affinity for plasma proteins was used to detect urinary proteins leaking into the ureter of zebrafish. Aristolochic acid exposure to fertilized eggs of transgenic zebrafish expressing green fluorescent protein from the proximal tubules to the excretory pore induced concentration-dependent renal dysfunction. The solvatochromic dye ZMB741 was applied via static immersion to analyze leaked dye-plasma-protein complexes in the ureter; their axial distribution was imaged by using confocal microscopy. The effect of resveratrol, an attenuator of aristolochic acid nephropathy, was further analyzed. This method enables individual-level analysis of podocytopathy, a mild glomerular disease that does not necessarily lead to the excretion of proteinuria. Moreover, it will be useful for pathophysiological studies of renal function and the identification of potential therapeutic drugs.