The Probe for Renal Organic Cation Secretion (4-Dimethylaminostyryl)-N-Methylpyridinium (ASP+)) Shows Amplified Fluorescence by Binding to Albumin and Is Accumulated In Vivo

Figure 2

Time series showing the fluorescence signal in the kidney cortex of a bolus injection of ASP+. To visualize the passage of the injected bolus through the renal structures, the image recorded at has been subtracted from the images recorded at each time point. 7.8 s: the bolus of ASP+ is visible in the glomerular capillaries (g), Bowman’s space (b), and in some peritubular capillaries (c) as well as in the very basal part of cells in the proximal tubule (x) adjacent to capillaries with visible ASP+. Proximal tubules in areas of the cortex in which the bolus has not yet reached the capillaries or tubular lumen (y) do not show ASP+ signal at this time. Scalebars: 50 μm .11.8 s: the proximal tubule labelled y begins to show basal ASP+ signal, and a strong ASP+ signal appears also in the brushborder of this proximal tubule. In the proximal tubule labelled x, the basal ASP+ signal now appears intracellular and diffuse. 12.7 s and 14.0 s: the strong ASP+ signal in the brushborder of tubule y spreads along the tubule and diffuse intracellular signal develops. 18.5 s: the strong ASP+ signal in the brush border of tubule y gradually diminishes but the diffuse intracellular signal remains. 180 s: the signal from the bolus of ASP+ is no longer evident.