Maternal hepatic and embryonic effects of 1,2,4-trichlorobenzene in the rat

The possible maternal hepatic and reproductive effects of 1,2,4-trichlorobenzene (TCB) were assessed in rats given 0, 36, 120, 360, and 1200 mg/kg/day of TCB on Days 9-13 of gestation. The animals were sacrificed on Day 14 of pregnancy. Maternal deaths (2/9 rats, 6/6 rats) were recorded in the 360 and 1200 mg/kg/day treatment groups and body weight gain was significantly decreased in the 360 mg/kg/day TCB group. Maternal liver weight, liver/body weight ratio, and hepatic microsomal protein content were unaffected by TCB treatment. Although Day 14 NADPH-cytochrome c reductase activity was affected only at 360 mg/kg/day TCB, the maternal hepatic microsomal cytochrome P-450 content was significantly increased by administration of both 120 and 360 mg/kg/day of TCB. Hepatic microsomal aminopyrine N-demethylase, ethoxyresorufin O-deethylase, and UDP-glucuronyl transferase activity towards p-nitrophenol were also increased at 120 and 360 mg/kg TCB. Glutathione S-transferase activity to 1-chloro-2,4-dinitrobenzene and 1,2 dichloro-4-nitrobenzene were both increased by pretreatment with TCB. Although pretreatment with 360 mg/kg/day TCB did not increase resorptions, embryolethality, or teratogenicity, embryonic development was significantly retarded by all four growth criteria used (head length, crown-rump length, somite number, and protein content).