Measurement of pancreatic lipase activity in serum by a kinetic colorimetric assay using a new chromogenic substrate

Abstract

We evaluate a new assay reagent for lipase determination, based on the use of 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6'-methylresorufin) ester (DGGR) as substrate. DGGR is cleaved by lipase, resulting in an unstable dicarbonic acid ester which is spontaneously hydrolysed to yield glutaric acid and methylresorufin, a bluish-purple chromophore with peak absorption at 580 nm. The rate of methylresorufin formation is directly proportional to the lipase activity in the sample. Bile salts, colipase and calcium chloride are included to provide optimal reactivity and specificity. Analysis of total imprecision gave a coefficient of variation of between 5.7% and 9.6%. Anticoagulants, common interfering substances and carboxylesterase had no effect on the assay, but interference by increased concentrations of serum triglycerides was noted. Good correlations were obtained with turbidimetry and a coupled enzymatic method. The estimated reference interval was 6-38 U/L. The unique characteristics of the chromogenic substrate qualify the present method as an innovative approach to serum lipase analysis.