Uptake of [(3)H]bilirubin in freshly isolated rat hepatocytes: role of free bilirubin concentration |
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Authors: | Mediavilla M G Pascolo L Rodriguez J V Guibert E E Ostrow J D Tiribelli C |
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Institution: | Centro Studi Fegato, Department of Biochemistry, Biophysics and Chemistry of Macromolecules (BBCM), University of Trieste, Via Giorgeri 1, 34127, Trieste, Italy. |
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Abstract: | Hepatocytic transport of physiological concentrations of unconjugated bilirubin (UCB) has not been determined in isolated liver cells. Initial uptake of highly purified (3)H]UCB was measured in rat hepatocytes in the presence of human serum albumin at various free, unbound UCB concentrations, UCB]. At UCB]=42 nM (below aqueous solubility of 70 nM), uptake was strictly temperature dependent; this was much less evident at UCB]=166 nM (supersaturated). At low, physiological UCB concentrations, specific UCB uptake showed saturative kinetics with an apparent K(m) of 41 nM, indicating carrier-mediated transport. With aqueous supersaturation, UCB entered hepatocytes mainly by passive diffusion. |
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