We tested the hypothesis that apolipoproteins, the protein constituents of plasmalipoproteins, are secreted into bile. We examined human gallbladder bile obtained at surgery (N=54) from subjects with (N=44) and without (N=10) gallstones and hepatic bile collected by T-tube drainage (N=9) after cholecystectomy. Using specific radioiimmunoassays for human apolipoproteins A-I and A-II, the major apoproteins of high density lipoproteins, for apolipoproteins C-II and C-III, major apoproteins of very low density lipoproteins, and for apolipoprotein B, the major apoprotein of low density lipoproteins, we found immunoreactivity for these five apolipoproteins in every bile sample studied in concentrations up to 10% of their plasma values. Using double immunodiffusion, we observed complete lines of identity between bile samples and purified apolipoproteins A-I, A-II, or C-II. Using molecular sieve chromatography, we found identical elution profiles for biliary apolipoprotins A-I, A-II and B and these same apolipoproteins purified from human plasma. When we added high density lipoproteins purified from human plasma. When we added high density lipoproteins purified from human plasma to lipoprotein-free solutions perfusing isolated rat livers, we detected apolipoproteins A-I and A-II in bile. Similarly, when we added low density lipoproteins purified from human plasma to lipoprotein-free solutions perfusing isolated livers of rats treated with ethinyl estradiol in order to enhance hepatic uptake of low-density lipoproteins, we found apolipoprotein B in bile. These data indicate that apolipoproteins can be transported accros the hepatocyte and secreted into bile.
|Original language||English (US)|
|Number of pages||11|
|Journal||Journal of Lipid Research|
|State||Published - 1983|
ASJC Scopus subject areas
- Cell Biology