Characterization of bilirubin transport system by human peripheral blood mononuclear cells

• Published in: Journal of leukocyte biology Vol. 51; no. 1; pp. 2 - 6
• Main Authors: Haga, Yoshio, Tempero, Margaret A., Kay, H. David, Zetterman, Rowen K.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Society for Leukocyte Biology 01.01.1992; Federation of American Societies for Experimental Biology
• Subjects: Adult; Azides - pharmacology; bilirubin; Bilirubin - pharmacokinetics; Biological and medical sciences; Biological Transport - physiology; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone - pharmacology; Cells, Cultured; Dose-Response Relationship, Drug; Energy Metabolism - drug effects; Energy Metabolism - physiology; Flow Cytometry; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Humans; Immunobiology; jaundice; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - metabolism; Leukocytes, Mononuclear - physiology; liver disease; lymphocytes; Lymphoid cells: ontogeny, maturation, markers, receptors, circulation and recirculation; Middle Aged; monocytes; Oligomycins - pharmacology; Sodium Azide; Temperature; Time Factors; Human; Monocyte; Transportation system; Biological transport; Bilirubin; Lymphocyte; Blood
• ISSN: 0741-5400; 1938-3673
• DOI: 10.1002/jlb.51.1.2

Decreased immune responses have been observed in hyperbilirubinemic patients. This study investigates bilirubin transport into human peripheral blood mononuclear cells (PBMNCs). In vitro incubation of PBMNCs at 37° with 0–12 mg/dl bilirubin in solution with a fixed bovine serum albumin (BSA) concentration (3.0 g/dl) resulted in a dose‐dependent increase of intracellular bilirubin in both monocytes and lymphocytes. Bilirubin uptake in monocytes was significantly higher (up to 2.7 times) than in lymphocytes under the same culture conditions. When PBMNCs were incubated with varying concentrations of bilirubin (0–16 mg/dl) in fixed BSA (3.0 g/dl) solution or at a fixed bilirubin/albumin molar ratio (0.4), the initial velocity of uptake in both cell fractions was proportional to the free (unbound to albumin) bilirubin concentration rather than the total bilirubin concentration. Bilirubin uptake by both cell fractions was significantly inhibited by treatment with metabolic inhibitors. Bilirubin uptake by monocytes continued to increase in parallel with incubation temperature from 0° to 40°, whereas uptake by lymphocytes reached a maximal level at 20° and remained constant thereafter. These results suggest that monocytes and lymphocytes incorporate bilirubin in proportion to the free bilirubin concentration and this function may rely on different energy‐dependent mechanisms.