4-[125I] iodophenyltrimethylammonium ion, an iodinated acetylcholinesterase inhibitor with potential as a myocardial imaging agent.

4-[125I]Iodophenyltrimethylammonium acetate (4-I-125 PTMA) was prepared by chloramine-T iodination of N,N-dimethylaniline and subsequent methylation with methyliodide. Purification by thin layer chromatography afforded a product whose specific activity approached the theoretical carrier-free level. Biodistribution studies in normal ICR mice showed a significant accumulation of 4-I-125 PTMA in the heart tissue, with heart-to-blood ratios of 12.5, 10.4, 7.8, 3.4, 3.4, and 3.3 at 1, 5, 10, 30, 60, and 120 min, respectively. Initial uptake in the heart was greater than 26% of the injected dose per gram. Twenty-five percent of the activity was excreted unchanged by the kidneys during the first 5 min. Less than half of the injected activity was retained in mice at 120 min.