Effect of Albumin Binding on Bilirubin Conjugation and Toxicity in Cell Culture of a Clonal Strain of Rat Hepatoma Cells

Abstract

A clonal strain of rat hepatoma cells (MH₁C₁) known to take up and conjugate bilirubin was incubated in media containing bilirubin and albumin in different molar ratios at a constant bilirubin concentration. The highest rate of bilirubin conjugation was found at a molar ratio of 1/1. Excess bilirubin markedly reduced both the conjugation of bilirubin and the incorporation of [¹⁴C]alanine, indicating a toxic effect on the cells. Excess albumin also depressed the formation of bilirubin conjugates, but incorporation of [¹⁴C]alanine proceeded at a normal rate, indicating that the reduced conjugation is probably due to stronger binding of bilirubin to albumin and reduced cellular uptake of bilirubin. Bilirubin bound to albumin at a molar ratio of 1/1 had no toxic effects on the cells as judged by cell morphology and conjugation capacity, even at a total bilirubin concentration as high as 680 μmol/l.

Key Words:

• Albumin
• bilirubin
• cell culture
• conjugation
• toxicity