Site-specific/stable radioiodination of 1,2-Pal-3-IPPA: an agent for the potential clinical evaluation of pancreatic insufficiency by urine analysis.

To measure pancreatic lipase activity, we synthesized a triglyceride containing a radioiodinated fatty acid. The urinary excretion of radioactivity was measured in five rats following administration of the agent by feeding tube. We attached 15-phenylpentadecanoic acid (PPA) to position-3 of 1,2-dipalmitoyl-rac-glycerol (1,2-Pal) to form 1,2-Pal-3-PPA. The 1,2-Pal-3-IPPA (expected lipase substrate) was prepared by the thallation-iodide displacement method. In a dual-label study, the 125 I-1,2-Pal-3-IPPA triglyceride was administered with the 131 I-IPPA free acid to rats (n=5) by oral gavage. Urine and feces were collected daily and the tissue distribution of both tracers was evaluated over a fiveday period