OAT3-mediated extrusion of the 99mTc-ECD metabolite in the mouse brain

After administration of the Tc-99m complex with N,N'-1,2-ethylenediylbis-L-cysteine diethyl ester (Tc-99m-ECD), a brain perfusion imaging agent, the radioactive metabolite is trapped in primate brain, but not in mouse and rat. Here, we investigate the involvement of metabolite extrusion by organic anion transporter 3 (OAT3), which is highly expressed at the blood brain barrier in mice, in this species difference. The efflux rate of radioactivity in the cerebrum of Oat3(-/-) mice at later phase was 20% of that of control mice. Thus, organic anion transporters in mouse brain would be involved in the low brain retention of radioactivity after Tc-99m-ECD administration.