Nuclear Medicine Program progress report for quarter ending March 31, 1993

We have exploring the possibility of measuring urinary radioactivity as an index of pancreatic lipase activity after oral administration of a new triglyceride containing a radioactive iodine-1 25-labeled fatty acid moiety. The new agent, 1,2-dipalmitoyl-3[15-(p-iodophenyl)pentandecan-l-oyl]-racglycerol (1,2-Pal-3-IPPA), was prepared by the thallation-iodide displacement method. Following oral gavage of the radioiodinated triglyceride to rats, about 30% of the administered activity was excreted in 24 hours in the urine. In normal human controls an higher urinary excretion (of about 75% was observed. In this report, we describe an evaluation of the metabolites excreted in the urine and the chemical species stored in adipose from rats. The urine activity co-chromatographed with hippuric acid by TLC indicating conjugation of the IPPA metabolites. Release of the acidic components from the conjugated excretory products by acid hydrolysis of the urine provided the radioactive acidic IPPA metabolites. Analysis of the Folch extracts of fat samples from rats demonstrated that the radioactive components co-chromatographed In the triglyceride region. Recent studies in patients with compromised pancreatic exocrine function have demonstrated significantly decreased 24 hr. urinary excretion of about 25%, following oral administration of [1 -1 31]-1,2-Pal-3-IPPA. Thus, urine analysis after oral administration of [I -1 31]-1,2-Pal-3-IPPA may be a simple,more » non-invasive tool for the clinical evaluation of various diseases involving dietary fat digestion.« less