Serum Lipase Determination with an Olive Oil Substrate Using a Three-Hour Incubation Period

The effect of various emulsifying agents, pH, buffers, and accelerators on the Cherry-Crandall procedure for determining serum lipase was studied. A method is proposed which uses a 3-hour incubation period. Olive oil emulsified with 7 % acacia is the substrate. This is buffered with tris buffer, pH 8.0; magnesium acetate and EDTA are added as accelerators. Other conditions which result in an increased rate of hydrolysis are discussed. 1T1E DETERMINATION of serum lipase levels is generally recognized to be a valuable aid in the diagnosis of acute pancreatitis (1-3). Follow-ing an attack of acute pancreatitis, lipase remains elevated in blood after the amylase level has returned to normal. The Cherry-Crandall (4) procedure for determination of serum lipase has been in general use for many years, and is the basis of the method in Standard Meth-ods of Clinical Chemistry (5). The inherent disadvantage of this tech-nic is the required 16- to 24-hour incubation period (6). Methods have been proposed requiring a shorter time of incubation. Bunch and Emerson (7), using what is essentially the Nothman, Pratt, and Benot-ti (8) procedure, found adequate amounts of hydrolysis after 4 hours’ incubation-provided the enzyme level was elevated. Tietz (9), using olive oil with barbiturate buffer at pH 8.0, was able to obtain sufficient hydrolysis for satisfactory determination after 6 hours ’ incubation. Olive oil has generally been used as the substrate. Other substrates proposed include tributyrin (10), alpha naphthyl laurate (ii), beta naphthyllaurate (12,13), phenyllaurate (14), and Tween 20 (15)