Abstract
The objective of this study was to establish a new lipoprotein lipase (LPL) and hepatic lipase (HL) activity assay method. Seventy normal volunteers were recruited. Lipase activities were assayed by measuring the increase in absorbance at 546 nm due to the quinoneine dye. Reaction mixture-1 (R-1) contained dioleoylglycerol solubilized with lauryldimethylaminobetaine, monoacylglycerol-specific lipase, glycerolkinase, glycerol-3-phosphate oxidase, peroxidase, ascorbic acid oxidase, and apolipoprotein C-II (apoC-II). R-2 contained Tris-HCl (pH 8.7) and 4-aminoantipyrine. Automated assay of lipase activities was performed with an automatic clinical analyzer. In the assay for HL + LPL activity, 160 microl R-1 was incubated at 37 degrees C with 2 microl of sample for 5 min, and 80 microl R-2 was added. HL activities were measured under the same conditions without apoC-II. HL and LPL activities were also measured by the conventional isotope method and for HL mass by ELISA. Lipase activity detected in a 1.6 M NaCl-eluted fraction from a heparin-Sepharose column was enhanced by adding purified apoC-II in a dose-dependent manner, whereas that eluted by 0.8 M NaCl was not. Postheparin plasma-LPL and HL activities measured in the present automated method had high correlations with those measured by conventional activity and mass methods. This automated assay method for LPL and HL activities is simple and reliable and can be applied to an automatic clinical analyzer.
Highlights
The objective of this study was to establish a new lipoprotein lipase (LPL) and hepatic lipase (HL) activity assay method
The lipase activities in the fraction eluted in 0.8 M NaCl were not enhanced at all in the presence of apolipoprotein C-II (apoC-II), indicating that the activities in this fraction derived from HL, whereas those eluted 1.6 M NaCl were enhanced in a dose-dependent manner, reaching a maximum at an apoC-II concentration of 5 mg/ml (Fig. 3A)
We have described an automated kinetic colorimetric method for assaying LPL and HL activities in postheparin plasma (PHP) by using a natural long-chain fatty acid, 1,2-diglyceride
Summary
The objective of this study was to establish a new lipoprotein lipase (LPL) and hepatic lipase (HL) activity assay method. HL and LPL activities were measured by the conventional isotope method and for HL mass by ELISA. Postheparin plasma-LPL and HL activities measured in the present automated method had high correlations with those measured by conventional activity and mass methods This automated assay method for LPL and HL activities is simple and reliable and can be applied to an automatic clinical analyzer.—Imamura, S., J. The conventionally available method for measuring LPL and HL activity has been the use of 3H- or 14C-labeled trioleoyl glycerol as substrate in the presence of 1 M NaCl or the anti-LPL monoclonal antibody, 5D2 [10, 11]; remaining activity is considered to be HL activity under these conditions This assay procedure is complicated and is not suitable for routine clinical or research work.
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