Effect of phenobarbital on adult rat liver cells treated with 3'-methyl-4-dimethylaminoazobenzene in primary culture.

The effect of phenobarbital (PB) on liver cells treated with 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) was studied using primary cultures of normal adult rat liver cells. Following a 1-day attachment period, primary liver cell cultures were treated with 0.24 mM 3'-Me-DAB for 6 days, and then treated with or without PB at 0.75, 1.5 and 3 mM for 19 days. Similarly, control cultures were treated with 0.5% dimethylsulfoxide (DMSO), a solvent for 3'-Me-DAB, for 6 days, and then treated with or without PB in the same way. Each treatment was done on 8 cultures. Chromosome analysis and cytochemical assay for gamma-glutamyltranspeptidase (GGT) activity were carried out on the carcinogen-treated and control cultures between 1 and 2 months after initiation of primary culture. Chromosomal abnormalities were detected in 23 of 32 carcinogen-treated cultures and also in 2 of 28 control cultures tested. However, GGT positive cells were detected only in the carcinogen-treated cultures at a frequency of 22/32. Of the 23 carcinogen-treated cultures with chromosomal abnormalities, 18 contained GGT positive cells. These results show a good correlation between chromosomal abnormality and acquisition of GGT activity at culture dish level. Furthermore, in the carcinogen-treated cultures, PB treatment caused a dose-dependent increase in the number of GGT positive cultures and in the percentage of GGT positive cells in each culture, and also caused a dose-dependent increase in the number of cultures with chromosomal abnormalities.