Characterization of the binding of [125I]L-735,286: a new nonpeptide angiotensin II AT1 receptor radioligand.

[125I]L-735,286, a new potent and AT1-selective nonpeptide angiotensin II receptor radioligand, bound saturably to whole adrenal membranes. Scatchard and Hill plot analysis indicates a single class of high affinity (Kd = 0.5 nM) binding sites. The potencies of various angiotensin II agonists and antagonists in displacing specific [125I]L-735,286 binding are in good agreement with their potencies in displacing the binding of [125I]Sar1,Ile8-AII to adrenal AT1 receptors. The AT2 selective ligand, PD121981 had no effect on specific [125I]L-735,286 binding. In autoradiographic studies using rat kidney slices, specific labeling of [125I]L-735,286 was abolished by coincubation with saralasin. Collectively, the data indicated that [125I]L-735,286 represents a new, potent nonpeptide antagonist radioligand suitable for the study of angiotensin II AT1 receptors.