This study deals with the application of the previously developed immo
bilized and perfused isolated hepatocytes as a cellular system for the
study of representative phase I and phase II of biotransformation rea
ctions. To illustrate phase I reactions, aminopyrine (0.17-4.25 mmol/l
) and hexobarbital (0.2 mmol/l) were selected. For phase II reactions,
glutathione transferase activity was evaluated by using 1-chloro-2,4-
dinitrobenzene (CDNB) as a substrate (0.125-2.0 mmol/l). Formaldehyde,
that was formed from aminopyrine, increased steadily in the perfusion
medium with time. The perfused hepatocytes eliminated hexobarbital at
a much higher rate than the hepatocytes in suspension. At several tim
e points the amount of CDNB-glutathione conjugate formed per one milli
on hepatocytes in the bioreactor was almost twice the amount formed by
the hepatocytes in suspension. The present data illustrate the succes
sful application of the hepatocyte bioreactor in phase I and phase II
of xenobiotic metabolism and indicate that the cells were metabolicall
y more active than the cells in suspension.