Sensitive detection of growth stimulating tumour promoters in perifused primary rat hepatocyte cultures.
Comparison of stationary cultivation with discrete changes of the medium with perifusion, where the hepatocytes are cultivated under a continuous flow of medium showed an enhanced sensitivity of perifused hepatocytes towards the mitogen cyproterone acetate (CPA) and the potential tumour promoters lindane, 4-chloro-1-naphthol, dieldrin and clofibrate. Addition of these substrates significantly stimulated DNA synthesis in the perifusion cultures while stationary cultures remained dormant or reacted in a less pronounced manner. In contrast, 1-methyl-3-nitro-1-nitroso-guanidine (MNNG) at 5 mum showed no effect on the incorporation of bromodeoxyuridine (BrdU) in both systems. The increase in sensitivity may be due to physical (establishment of steady-state concentrations) and physiological advantages (enhanced biotransformation, intact signal transduction pathways) of the perifusion culture. These studies demonstrate that perifusion is more suitable than stationary rat hepatocyte cultures with respect to the detection of growth stimulatory effects of tumour promoters, as previously reported for growth inhibitory effects of some genotoxic carcinogens. Therefore, the perifusion may considerably aid in discriminating between growth inhibitory and growth stimulatory effects of environmental chemicals.
Klein
S
S
Physiologisch-chemisches Institut der Universität Tübingen, D-72076 Tübingen, Germany.
Gebhardt
R
R