K. De Smet et al., Collagen type I gel cultures of adult rat hepatocytes as a screening induction model for cytochrome P450-dependent enzymes, ATLA-ALT L, 29(2), 2001, pp. 179-192
Albumin secretion, expression of cytochrome P450-dependent mono-oxygenases
(CYPs) and their inducibility by well-known inducers were evaluated during
1 week in collagen type I gel sandwich and immobilisation cultures of adult
primary rat hepatocytes. Albumin secretion increased during culture and, f
ollowing an initial decrease, CYP biotransformation activities remained sta
ble for at least 7 days. Better preservation results were observed in the c
ollagen gel sandwich culture than in the immobilisation model. The inducibi
lity of CYPs by beta -naphthoflavone (beta -NF). 3-methylcholanthrene (3-MC
), phenobarbital (PB) and dexamethasone (DEX) was studied in both collagen
gel hepatocyte cultures. Exposure of the cells to either 5 muM 3-MC or 25 m
uM beta -NF, added to the culture medium, resulted in strong increases of C
YP1A1/2 activity in both culture models. Treatment with PB (3.2mM) resulted
in an increase in the CYP2B activity and a higher hydroxylation of testost
erone in the 16 alpha -position (CYP2B1/2 and CYP2C11), the 7 alpha -positi
on (CYP2A1/2), and the 6 beta -position (CYP3A1). DEX (10 muM) markedly inc
reased testosterone 6 beta- and 7 alpha -hydroxylation. Expression and indu
ction experiments on CYP proteins exposed to these molecules confirmed the
results of the CYP activity measurements. The patterns of CYP induction in
collagen gel cultures of rat hepatocytes were similar to those observed in
vivo. Consequently, collagen gel cultures and, more specifically, collagen
gel sandwich cultures seem to be suitable as in vitro models for evaluating
xenobiotics as potential inducers of CYP-enzymes.