VARIATIONS IN PIGMENT AND CARBOHYDRATE CONTENT OF GALLBLADDER BILE AFFECT ACCURATE QUANTITATION OF TOTAL PROTEIN WHEN USING THE FLUORESCAMINE METHOD

Background: Despite solute dilution and reduced total lipid concentrat ions, an unexplained increase in protein concentration has been report ed to occur in the gallbladder bile of cholesterol gallstone patients. Methods: Solutes in gallbladder bile from gallstone-free controls and from four study groups were measured using standard methods. Total pr oteins were measured using amino acid analysis and a conventional fluo rescamine method. Results: Bile salts and pigment content were greater in gallstone-free controls than in all other study groups, including morbidly obese gallstone-free subjects. Total biliary protein concentr ation, as determined by amino acid analysis in the gallstone-free cont rol group was higher than in non-obese gallstone patients with multipl e stones and in morbidly obese gallstone-free subjects. Total biliary proteins as measured with fluorescamine, however, did not show intergr oup differences. A major problem of the conventional fluorescamine ass ay is shown to be an artefact arising from the high pigment content of the more concentrated samples. Conclusions: Very dilute gallbladder b ile samples are often found in the presence of gallstone disease. This also occurs in morbidly obese subjects, even in the absence of gallst ones. Although the contribution of protein secretion/absorption by the gallbladder can also be relevant, especially in the presence of morbi d obesity, the protein concentration in gallbladder bile, when accurat ely measured, generally parallels the concentrations of non-absorbed b iliary solutes, reflecting the efficiency of fluid absorption. Measure ment of biliary proteins by the conventional fluorescamine method is u nreliable in clinical studies in which intergroup differences in pigme nt content are commonly present.