Genetic Regulation of Aryl Hydrocarbon Hydroxylase in Primary Cultures of Fetal Cells Established from Inbred Strains of Mice¹

Primary cultures of fetal cells were established from six inbred strains of mice to determine whether genes regulating induction of aryl hydrocarbon hydroxylase (AHH) in livers in vivo also function in fetal cells maintained in vitro. Fetal cells were cultured from three inbred mouse strains that are classified genetically as aromatic hydrocarbon responsive (A/J, C3H/HeJ, and C57BL/6J), and three that are classified as aromatic hydrocarbon nonresponsive (AKR/J, DBA/2J, and SWR/J). Responsive strains produce a high-affinity protein receptor for polycyclic hydrocarbons, whereas nonresponsive strains do not. The time course of the induction of AHH activity by 0.1 µg 3-methylcholanthrene or 1.0 µg benzanthracene per ml of media was followed from the time cells were plated until cells reached confluency. During exponential growth phase, AHH activity in basal and induced cells increased, reached a plateau, and then gradually decreased as cells attained confluency and entered stationary growth phase. Fetal cells could be classified into two groups on the basis of whether they were from aromatic hydrocarbon-responsive or nonresponsive strains of mice. Ratios of induced AHH activity to basal AHH activity were determined during late exponential to early stationary growth phase. Values were near 1.0 for 3-methylcholanthrene-induced cells and 7 to 10 for benzanthracene-induced cells established from the three inbred strains of mice that are nonresponsive in vivo. Fetal cells cultured from the three inbred strains of mice that are responsive in vivo had ratios near 2.0 for 3-methylcholanthrene-induced cells and greater than 10 for benzanthracene-induced cells. AHH activities in both basal and induced fetal cells were inhibited by 7,8-benzoflavone, indicating that the major type of AHH is predominantly of the nonhepatic type. Our results indicate that the genes controlling aromatic hydrocarbon responsiveness in mouse livers in vivo also function in nonhepatic fetal cells in vitro.