Photometric microdetermination of serum lipase with a phenyl laurate substrate.

The Raderecht and Moskau procedure for pancreatic lipase (6) has been modified for determining the small amounts of this enzyme present in normal blood serum. The present investigation confirmed their findings: that phenyl laurate provides a stable easily-prepared substrate of uniform composition; that the substrate is specifically split by serum and pancreatic lipase; and that the reaction product (phenol) can be readily determined by a simple and sensitive colorimetric procedure. The lipase units are expressed in the same manner as are phosphataseunits; i.e., milligramsof phenol liberated per 100 ml. serum at 370 in 30 mm. The normal range, basedon 40 sera, was found to be 2.5-5.6 units. The serum lipase valueswere shown to be significantly elevated in a number of caseswith acute pancreatic disease. The advantage of this procedure over others presently employed for diagnosticevaluation of these conditions is discussed.