Journal of Lipid Research, Vol 22, 177-184, Copyright © 1981 by Lipid Research, Inc.
Optimization and validation of assays to estimate pancreatic esterase activity using well-characterized micellar solutions of cholesteryl oleate and tocopheryl acetate
PM Mathias, JT Harries and DP Muller
Studies have been carried out to determine the maximal solubilization of
cholesteryl oleate and tocopheryl acetate within mixed bile salt- fatty
acid micelles and to establish reproducible assays for pancreatic esterase
activity using these micellar substrates. At pH 8.5, using 30 mM sodium
taurocholate and 10 mM oleic acid, reproducible micellar solutions of the
esters could be prepared giving micellar concentrations of 0.4 mM and 0.1
mM for tocopheryl acetate and cholesteryl oleate, respectively. Conditions
were then optimized to estimate pancreatic esterase activity using these
micellar-solubilized substrates. Maximal activity was obtained at pH 8.5
with 2-4 mM oleic acid and 15-30 mM sodium taurocholate, and gave
coefficients of variation for the assays of 7.4% and 20.2% using tocopheryl
acetate and cholesteryl oleate, respectively, as substrates.
Micellar-solubilized cholesteryl oleate and tocopheryl acetate, together
with a non-micellar system using p-nitrophenyl acetate, were used to
estimate esterase activity in human duodenal aspirates and rat pancreatic
homogenates. Esterase activity in children with cystic fibrosis was greatly
reduced and paralleled tryptic and pancreatic lipase activity, which
suggested that the esterase activity was pancreatic in origin. The results
of this study, therefore, provide a basis for future investigations
concerned with the hydrolysis and absorption of dietary esters.
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