Technetium-99m-MAG3 as a transport substrate of rat renal organic anion transporter-1

The first step of technetium-99m-mercaptoacetylglycylglycylglycine (99mTc-MAG3) secretion by the proximal tubule cells is the extraction of 99mTc-MAG3 from the peritubular plasma by proximal tubule cells through the basolateral membrane. The evidence for 99mTc-MAG3 being excreted from renal proximal tubules via rat organic anion transporter 1 (OAT1) by molecular biological experiments with expressed OAT1 in Xenopus laevis oocytes was discussed. Inhibition studies of 99mTc-MAG3 revealed that OAT1 mediated Na+-independent 99mTc-MAG3 uptake, and that this transport was energy-independent. Accumulated dicarboxylate, such as glutarate, stimulated 99mTc-MAG3 uptake. Tc-99m-MAG3, as well as paminohippurate (PAH), and o-iodohippurate (OIH), was confirmed to be a transport substrate of OAT1 by the uptake of expressed oocytes.