Measurement of serum lipase activity with the oxygen electrode

We describe the measurement of lipase (triacylglycerol lipase; EC 3.1.1.3) in serum by continuous monitoring of relative rates of oxygen consumption with a polarographic oxygen electrode. The reactions described by Proelss and Wright (Clin. Chem. 23: 522-531, 1977) are used: trilinolein, with lipase catalysis, yields linoleic acid, which reacts with oxygen in the presence of lipoxygenase. Lipase activity is measured by comparing the zero order reaction rate of the specimen with that obtained with linoleic acid standards. Results for lipase (y) correlated well with those by the copper-soap method of Myrtle and Zell (x) (Clin. Chem. 21: 1469-1473, 1975); y = 0.33x - 11; r = 0.98; n = 34. Results are unaffected by specimen dilution, and the standard curve is linear to 520 U/L. Day-to-day precision (CV) is 10.4% for normal activities, 6.1% for above-normal activities. We believe the method offers a precise, practical approach to lipase analysis.