Nuclear medicine progress report for quarter ending September 30, 1984

The preparation and animal testing of a new radio-iodinated p-iodophenylamine-linked dihydropyridine system is described. The model agent, 1-methyl-3-(N-(..beta..-(4-(/sup 125/I)iodophenyl)ethyl)carbamoyl)-1,4-dihydropyridine, was prepared by coupling 4-(/sup 125/I)iodoaniline with the methiodide salt succinimidyl ester of nicotinic acid followed by dithionite reduction to the lipid soluble product. The dihydropyridine agent showed good brain uptake in rats (5 min, 1.14% injected dose/gm; 60 min, 1.12% dose/gm) and good brain to blood ratios (5 min 3.9:1, 60 min, 3.5:1). In contrast the quaternary ammonium compound, prior to reduction, showed only moderate brain uptake (5 min, 0.63; 60 min, 0.46) and low brain to blood ratios (5 min, 0.05; 60 min, 0.06). Also described is further investigation of the effects of fasting on the relative myocardial retention of straight-chain iodovinyl fatty acids. 18-(/sup 125/)Iodo-17-octadecenoic acid showed good retention in unfasted rats. Studies have now been reported for fasted rats where this agent showed rapid myocardial wash-out. In fasted rats, approx. 70% wash-out at 30 min, and in unfasted rats, approx. 15% wash-out at 30 min was observed. During this period several shipments were made to Medical Cooperative investigators including three samples of /sup 191/Os-potassium osmate (Children's Hospital, Boston, and the University of Liege, Belgium) and 15-(p-(/sup 131/I)iodophenyl)-3-R,S-methylpentadecanoicmore » acid (University of Massachusetts and Brookhaven National Laboratory).« less