Biodistribution experiments. Biodistribution studies of [125I]BH-exendin(9-39) were performed in male ddY mice. [125I]BH-exendin(9-39) (1 μCi) was administered by tail vein injection. At 15, 30, 60, and 120 min after administration, the mice were sacrificed by exsanguination under anesthesia. Selected JW55 and blood were harvested and weighed, and the radioactivities were measured with a γ-counter. In a blocking study, excess non-radioactive exendin(9-39) (50 μg) in 100 μl of saline was administered 30 min before the [125I]BH-exendin(9-39) injection. Results were expressed as percent radioactivity of injected [125I]BH-exendin(9-39) per gram of organ weight.
Two-dimensional imaging analysis. After intravenous administration of [125I]BH-exendin(9-39) to male MIP-GFP mice, the pancreas was harvested and cut in several pieces. Each piece was put on slide glass and pressed with a cover glass. Signals of fluorescence and radioactivity (autoradiography) of sections of pancreas were evaluated with an image analyzer (Typhoon 9410; GE Healthcare, Buckinghamshire, UK). The fluorescent and radioactive intensity of each section was analyzed with ImageQuant TL software with resolution of 25 and 10 μm per pixel, respectively (GE Healthcare).