- source of S9 : Male Wistar, HSdCpb:Wu rats from Harlan Winkelmann, Borchen, Germany, aged 6-8 weeks, were given a single intraperitoneal injection of Aroclor 1254 (500 mg/kg body weight) diluted in Miglyol 812 oil. The animals received drinking water and a standard diet ad libitum. About 16 hours before sacrifice, the feed was removed. Five to seven days after application of Aroclor, the rats were sacrificed and the livers collected in ice-cooled, sterilized beakers containing 0.15 M KCl. The livers were homogenized in a sterile glass potter homogenizer containing 3 ml of 0.15 M KCl per gram of liver wet-weight. The homogenate was spun at 9000 x g for 10 minutes at about +4°C and the supernatant fluid was decanted and transferred into sterilized and precooled plastic tubes. The S9 was then frozen in liquid nitrogen and stored at -196°C.