Evaluation of pancreatic lipase activity by simple urine analysis after oral administration of a new iodine-131-labeled triglyceride

A new iodine-131-labeled triglyceride analogue called “MIPAG” [1,2-dipalmitoyl-3-[(15-p-iodophenyl) pentadecan-1-oyl]rac-glycerol] has been prepared in which 15-(p-iodophenyl)pentadecanoic acid (IPPA) is attached to position-3. MIPAG has been developed for the evaluation of pancreatic exocrine function by simple urine analysis and has been evaluated in rats and humans. After oral administration, IPPA is released from the triglyceride by the action of pancreatic lipases followed by intestinal absorption and the principal IPPA metabolite (p-iodobenzoic acid, IBA) is primarily excreted in the urine. Excretion in the urine and feces was evaluated in rats, as well as the biodistribution in various organs over 21 days. Twenty patients without pancreatic disease (normals) and four patients with pancreatic insufficiency were also investigated. Following oral administration of 30 μCi of MIPAG, urine was collected for two successive 24-h periods. Blood samples were drawn and thin-layer chromatographic (TLC) analysis was performed on the serum lipid extracts. Urine from normals contained 44.9%±7.7% and 61.8%±8.4% of the administered activity after 24 and 48 h, respectively. The patients with pancreatic insufficiency excreted 13.1%±5.6% and 18.9%±6.2%, respectively, which was significantly decreased (P<0.001) compared with normals. The TLC profiles showed an increasing proportion of IBA with time. Urine analysis after oral administration of MIPAG thus appears to be an attractive new technique for the evaluation of pancreatic lipase activity by a simple urine analysis.