Imaging the adrenal medulla with an I-131-labeled antiadrenergic agent.

Tissue distributions of four antiadrenergic agents labeled with iodine-125 have been determined in dogs. [125I] ortho-iodobenzldimethyl-2-hydroxyethyl ammonium and [125I] ortho-iodobenzyldimethylethyl ammonium show highly selective uptake in the adrenal medulla. Studies of molecular structure-distribution indicate that both the nature of the cationic head and the ring position of the iodine atom greatly influence adrenal specificity. Distinct images of dogs' adrenal medulla have been obtained 4 days after i.v. injection of 1.5 mCi of [131I] ortho-iodobenzyldimethyl-2-hydroxyethyl ammonium.