Preparation of 6-125I-labeled amiloride derivatives.
Amiloride and certain of its derivatives are effective inhibitors of Na/H antiporters and of epithelial Na channels. We describe a simple method for the preparation of a variety of pharmacologically active 6-iodoamiloride derivatives that are labeled with 125I at high specific radioactivity. 6-Dechloroamiloride derivatives (bearing a hydrogen atom instead of the chlorine at the 6 position of the amiloride molecule) are reacted with 125ICl, prepared by the oxidation of the iodide in Na125I preparations. The 125I-labeled derivatives are separated from free 125I by anion exchange chromatography, or purified by thin layer chromatography. Both 6-dechloroamiloride and 5-(N-alkyl)-6-dechloroamiloride derivatives can be labeled by this method, with yields varying between 10 and 70%, depending on the ICl concentration and the structure of the 5-N-alkyl group. Efficient radiolabeling at high specific radioactivity also depends on the use of freshly prepared batches of 125I. Using carrier-free 125I, [125I]6-iodoamiloride and [125I]6-iodo-5-(N-tert-butyl)amiloride were prepared with yields of 27 and 22%, respectively. Potential applications of the 125I-labeled amiloride derivatives include ligand binding and affinity labeling experiments.
Cassel
D
D
Department of Biology, Technion-Israel Institute of Technology, Haifa.
Rotman
M
M
Cragoe
E J
EJ
Igarashi
P
P
D000584:Amiloride / Q000031:analogs & derivatives*; D002852:Chromatography, Ion Exchange; D002855:Chromatography, Thin Layer; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods*
D007457:Iodine Radioisotopes; D000584:Amiloride