Endocytosed albumin co-localized with lysosomes and was degraded in podocytes.

<p>Confocal microscopy image demonstrating co-localization of albumin and lysosomes in a podocyte treated with 1.5 mg/mL FITC-albumin and Cathepsin B Magic Red for 1 hour. FITC- albumin was excited with a 488 nm laser and Magic Red with a 633 nm laser. FITC-Albumin is labeled green (<b>A</b>) and Magic Red, which selectively localizes in lysosomes, is labeled red (<b>B</b>). Yellow fluorescence represents albumin and Magic Red co-localization (<b>C</b>). Scale bar is 20 µm. <b>D</b>) Representative Western blot demonstrating the time course of albumin degradation. Podocytes were treated with 1.5 mg/mL FITC-albumin for 1 h then washed. Cells were harvested at time zero, 15, 30, 45, and 60 min. Albumin abundance in cell lysates was quantified by Western blot analysis using an antibody to FITC. <b>E</b>) Densitometry demonstrating an exponential decrease in abundance of FITC-albumin over 60 minutes normalized to GAPDH and abundance at time zero (n = 4).