Proposed standard method for measuring lipase activity in serum by a continuous sampling technique.

A method is presented for measuring lipase activity in serum by use of either triolein or olive oil as substrate. The method requires 3 to 8 mm for each measurement and 5 to 8 mm for initial set-up. The reaction mixture is maintained at the optimum pH of 8.8 by automatic addition of sodium hydroxide (10 mmol/liter) with a ‘pH-Stat.” Amount of sodium hydroxide delivered per unit time reflects lipase activity. When reaction conditions-such as pH, substrate concentration, emulsifier concentration, and type and concentration of added bile salts-were made optimal, the reaction kinetics were zero order. Data presented indicate that adding sodium glycocholate prevents inactivation of lipase and does not lead to activation of this enzyme. Comparative studies, in which triolein and olive oil, respectively, are used as substrates show that triolein is the superior substrate for lipase, but olive oil can be substituted for triolein for routine clinical laboratory use. The suggested upper limit of normal is 200 and 160 U/liter for tnolein and olive oil substrates, respectively.