The Conjugation of Bilirubin by Rat Hepatoma Cells in Tissue Culture 1

Summary The rat hepatoma cell strain H4-II-E, derived from the Reuber hepatoma H-35 and maintained in vitro for 12 years, takes up and conjugates bilirubin and excretes it into the culture medium at the rate of from 2.6 to 3.3 μg/mg cell protein/ hr when supplied with unconjugated bilirubin at 5 mg/100 ml and a bilirubin/ albumin molar ratio of 0.75. The conjugate identity was confirmed by comparison with conjugated bilirubin from human gall bladder bile by paper chromatography. HeLa cells, rat and human fibroblasts did not conjugate bilirubin. Seventeen clones were isolated from the parent culture, and all conjugated bilirubin. The mean conjugating rate of all clonal cultures was 4.1 ± 0.8 μg/mg/hr (mean ± SD, N = 43), compared with 3.0 ± 0.5 μg/mg/hr (N = 17) for the parent culture, a significant difference at the 1% level, possibly reflecting a selective effect of the cloning process for high conjugating capacity. This cell line and its subclones represent new examples of strains of cells in culture which metabolize bilirubin. Determination of fetal calf serum albumin content by Dr. Roy W. Bonsnes, Director, Laboratory for Clinical Chemistry, The New York Hospital, is gratefully acknowledged.