New procedure for the measurement of pancreatic lipase activity in human serum using a thioester substrate

Background: Definitive substrates for the measurement of pancreatic Lipase activity in human serum have not been conclusively identified owing to poor aqueous solubility and nonspecific susceptibility of substrates with existing methods. Thus, it is still important to propose new substrates for robust Lipase measurements.

Methods: Reaction conditions were studied for a Lipase method using newly synthesized 2,3-dibutyrylthio-1-propyl oleate as the substrate and 5,5'-dithio-bis-(2-nitro-benzoic acid) as the chromogen.

Results: Optimum conditions, using colipase and Mg(++) in aqueous hexamethyl phosphoric triamide medium at pH 9.2, were defined. The substrate was highly selective to pancreatic Lipase. The reaction increased linearly with Lipase concentrations up to 500 U/l. The reference interval of serum Lipase concentrations was 21.5-65 U/l. Using the Passing-Bablok regression analysis, the present assay shows a slope of 0.414, an intercept of -2.4 U/l, and r-value of 0.992 in the comparison with the chromogenic method using the 6-methylresorufin ester of 1-O,2-O-dilauryl-rac-glycero-3-glutaric acid as the substrate.

Conclusion: Because of the simple composition of the reagents, the proposed procedure may represent a significant advancement in the commercially available methods for pancreatic Lipase determination.