Figure 4. Biodistribution of Xentry, and a Xentry-β-galactosidase conjugate intravenously injected into mice.

(a) The hairless extremities of mice (right photograph) intravenously injected with 5 mg of Cy7 (red)-labelled Xentry assumed a bright red colour under natural light, compared to those of uninjected mice (left photograph). Mice were intravenously injected with 1 mg of Cy7-labelled Xentry, and the fluorescence of the whole bodies (b) and major organs (c) were recorded using the Xenogen-IVIS® Kinetic-In Vivo Imaging System, and compared with untreated control littermates. Dorsal, ventral and side views of representative mice are shown. The relative levels of fluorescence of the organs were plotted. The organs are in numerical order starting with heart (1) and ending with brain (11) as in the vertical listing. Mice were intravenously injected with 1 mg of TAMRA-labelled Xentry and the fluorescence of organ homogenates (d) and sections (e) was measured 15 min, 1, 6, and 24 h later. The relative levels of fluorescence of the organs were plotted as the mean ± SD (n = 3). (f) Mice were intravenously injected with 1 mg of β-galactosidase conjugated to Xentry, and β-galactosidase activity in sections of organs collected at 15 min, 1 and 6 h was visualized by staining tissue sections with the β-galactosidase substrate X-gal (blue).