A new type of bioartificial liver using isolated hepatocytes immobilized in alginate beads was developed and its capacity of correcting the metabolic deficiency of bilirubin conjugation in Gunn rats was assessed. Hepatocytes were isolated from Sprague-Dawley rats using the in situ collagenase perfusion technique, and they were then immobilized in Calcium alginate beads. The capacity of these immobilized hepatocytes to conjugate in vitro bilirubin was checked as compared to monolayer hepatocyte culture. The bioartificial liver consisted in a cylindrical bioreactor containing either alginate beads and hepatocytes (test group), or only alginate beads (control group). Gunn rats were connected to this bioreactor through and extracorporeal circulation system, and "bile samples were collected" every hour. Bilirubin mono and biconjugates were dosed in the bile using the high-performance liquid chromatography technique. The viability of alginate immobilized hepatocytes, determined before and after each experiment, was stable at 75%. In the test group, the total conjugate concentration rapidly increased to reach a maximum value of 204 +/- 16 microns after 3 hours, while in the control group, there were only conjugate traces (1 micron). These results show that the bioartificial liver is an efficient means to temporarily correct genetic deficiency in Gunn rats. Such a system could be of therapeutic interest in case of acute hepatic insufficiency.