Fig. 5. Renal clearance of tracers occurs within the proximal pronephric duct. Wild-type embryos (72 hpf) were injected with 10kDa-RD (red), 70kDa-FD (green), Cy2-RAP (green) or 500kDa-FD (green), and renal clearance of tracer into the pronephric-duct tubular cells was evaluated 1.5 hours later on (A) whole mounts or (B-G) transversal sections by confocal fluorescence microscopy. There is no tubular uptake of the 500kDa-FD tracer (D). Partial colocalization of 70kDa-FD and Rab4 (red) can be seen in endosomes of tubular cells of the pronephric duct that were immunostained for the early endosomal marker Rab4 (E-G). White dotted lines demarcate the position of the pronephric ducts in (B-D) or the outline of the pronephric duct lumen (E-G). Bars, 5 µm.