Journal of Lipid Research, Vol 29, 1055-1063, Copyright © 1988 by Lipid Research, Inc.
Biliary proteins: assessment of quantitative techniques and comparison in gallstone and nongallstone subjects
K Yamazaki, SP Powers and NF LaRusso
Gastroenterology Research Unit, Mayo Medical School, Rochester, MN 55905.
Although protein is the third most abundant solid in bile and is important
in cholesterol crystal formation, methods for quantitating the
concentration of total protein in bile have not been systematically
evaluated. To establish a reliable protein assay for bile, we evaluated
three protein assays (Lowry's method and the fluorescamine and Coomassie
blue methods), and employed amino acid analysis as a reference technique.
Large protein-to-protein variations were observed with the fluorescamine
and Coomassie blue methods. Although all assays were affected by
interfering substances, Lowry's method and the fluorescamine technique
(after trichloroacetic acid precipitation and delipidation of bile) and the
Coomassie blue method with native bile showed excellent correlations (P
less than 0.0001) with those obtained by amino acid analysis. Using these
reliable protein assays, we examined gallbladder bile obtained at surgery
from subjects with and without gallstones. No differences in the
concentrations of total biliary proteins were observed among patients with
cholesterol (n = 23) or pigment (n = 7) gallstones and subjects without
gallstones (n = 10). Protein values obtained by amino acid analysis also
did not differ among groups. As expected, bile from patients with
cholesterol gallstones was supersaturated with cholesterol while bile from
nongallstone subjects and those with pigment stones was unsaturated. These
results indicate that it is not possible to separate patients with and
without gallstones on the basis of the total protein concentration of
gallbladder bile.
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