A COMPARISON OF 2 METHODS TO MEASURE AMYLASE, LIPASE, TRYPSIN, AND CHYMOTRYPSIN ACTIVITY AND THE EFFECT OF FREEZING AND THAWING ON ENZYME-ACTIVITIES IN PANCREATIC-JUICE

An experiment was conducted to compare two methods, referred to as A a nd B, for measuring amylase, lipase, trypsin, and chymotrypsin activit ies in samples of pancreatic juice and to investigate the effect of fr eezing and thawing on enzyme activities. Three growing pigs were used in this study. A catheter was surgically inserted into the pancreatic duct and a simple T-cannula was placed in the duodenum to allow the re turn of collected pancreatic juice. Pancreatic juice was collected for a total of 24 h and 27 pooled 8-h samples were used in the analyses. Following collection and pooling, the samples were frozen at -80 degre es C, due to the large number of samples and analyses, and stored for 2 weeks. The samples were thawed and enzyme activities were determined with Method A. The samples were frozen again at -80 degrees C, stored for 2 weeks, and rethawed and enzyme activities were determined with Methods A and B. There was a direct relationship between Method A and Method B for measuring amylase, trypsin, and chymotrypsin activity (R- 2 = 0.95, 0.81, and 0.90, respectively). However, a poor relationship was observed between a titrimetric and a photometric method for determ ining lipase activity (R-2 = 0.42). A second freezing, storage, and th awing did not affect (p > 0.3) the concentration of protein or amylase activity in pancreatic juice. However, the activities of chymotrypsin , trypsin, and, especially, lipase were decreased by 29.0% (p < 0.11), 40.4% (p < 0.01), and 82.9% (p < 0.001), respectively. In conclusion, either Method A or Method B can be used to measure amylase, trypsin, and chymotrypsin activities in pancreatic juice but a titrimetric meth od should be used to determine lipase activity. Furthermore, if the ac tivities of lipase, trypsin, and chymotrypsin are to be determined, th e sample should only be frozen and thawed once. If amylase activity wi ll be determined, the sample can be repeatedly frozen and thawed.