4-CHLORO-O-PHENYLENEDIAMINE - A 26-WEEK ORAL (IN FEED) MUTAGENICITY STUDY IN BIG BLUE(TM) MICE

4-Chloro-o-phenylenediamine (4-C-o-PDA) is a liver carcinogen in mice and was found to be weakly mutagenic in the liver of female Big Blue(T M) mice after short term treatment. In the present study the test comp ound was given subchronically in the diet for 26 weeks at doses of 0, 5000 and 10,000 ppm. The corresponding average test substance intake w as 2166 mg kg(-1) day(-1) (males: 1794 mg kg(-1) day(-1); females: 253 9 mg kg(-1) day(-1)) and 4610 mg kg(-1) day(-1) (males: 3926 mg kg(-1) day(-1); females 5925 mg kg(-1) day(-1)) at the low and high dose, re spectively. After sacrifice, tissues were flash frozen in liquid nitro gen. The lad mutant frequency in the liver was determined from three m ale and three female mice per dose group. The genomically integrated t ransgene was recovered by packaging into lambda phage using Transpack( TM) packaging extract (Stratagene, La Jolla, USA) followed by infectio n of Escherichia coli strain SCS-8. Blue mutant plaques were scored ag ainst a background of clear non-mutant plaques. Food consumption decre ased initially at 10,000 ppm, while no treatment related effect on foo d intake was observed at 5000 ppm. Body weight gain was found to be de creased in all treated animals. Absolute and relative liver weight inc reased in a dose-related manner, but only the latter effect was statis tically significant. A clear dose dependent increase in lad mutant fre quencies was observed in the liver of both sexes. The following mutant frequencies (x 10(-5)) were observed: 2.73 +/- 1.01 (males, untreated ), 7.24 +/- 1.50 (females, untreated), 18.91 +/- 5.30 (5000 ppm, males ), 24.91 +/- 7.58 (5000 ppm, females), 20.47 +/- 6.68 (10,000 ppm, mal es) and 36.17 +/- 14.98 (10,000 ppm, females). It is therefore conclud ed that 4-C-o-PDA is a strong mutagen in the liver of mice treated sub chronically for 26 weeks. (C) 1998 Elsevier Science B.V. All rights re served.