Quantitative whole-body autoradiography (QWBA)

Tissue distribution was assessed based on QWBA of [³⁵S]-RGLS4326-derived radioactivity in male CD-1 mice following a single subcutaneous (SC) dose of RGLS4326 at 30 mg kg⁻¹ and a target radioactivity of 100 μCi kg⁻¹. At approximately 48 and 672 h post dose, mice were euthanized, and carcasses were submerged in a dry ice/hexane bath. The frozen carcasses were individually set in a mold, submerged in 5% (w v⁻¹) low viscosity carboxymethylcellulose (CMC), and embedded by placing the stage (mold) in a dry ice/hexane bath. Frozen blocked carcasses were removed from dry ice/hexane bath, and 1/4-inch holes were drilled into the sample blocks and filled with calibration standards containing known quantities of [³⁵S]-RGLS4326, prior to sectioning. Thirty microns thick sagittal sections of the CMC-embedded mouse carcasses, including calibration standards were sectioned and imaged using phosphor imaging plates. Autoradioluminograms of the sections were compared to calibration standards to obtain a measurement of the concentration of [³⁵S]-RGLS4326.