title: Tolerance of aged Fischer 344 rats against chlordecone-amplified carbon tetrachloride toxicity.
abstract: We have investigated the effects of chlordecone 1(CD)+CCl4 combination in adult (3 months), middle aged (14 months), and old aged (24 months) male Fischer 344 (F344) rats. After a non-toxic dietary regimen of CD (10 ppm) or normal powdered diet for 15 days, rats received a single non-toxic dose of CCl4 (100 microl/kg, i.p., 1:4 in corn oil) or corn oil (500 microl/kg, i.p.) alone on day 16. Liver injury was assessed by plasma ALT, AST, and histopathology during a time course of 0-96 h. Liver tissue repair was measured by [3H-CH3]-thymidine (3H-T) incorporation into hepatic nuclear DNA and proliferating cell nuclear antigen (PCNA) immunohistochemistry. Hepatomicrosomal CYP2E1 protein, enzyme activity, and covalent binding of 14CCl4-derived radiolabel were measured in normal and CD fed rats. Exposure to CCl4 alone caused modest liver injury only in 14- and 24-month-old rats but neither progression of injury nor mortality. The CD+CCl4 combination led to 100% mortality in 3-month-old rats by 72 h, whereas none of the 14- and 24-month-old rats died. Both 3- and 14-month-old rats exposed to CD+Cl4 had identical liver injury up to 36 h indicating that bioactivation-mediated CCl4 injury was the same in the two age groups. Thereafter, liver injury escalated only in 3-month-old while it declined in 14-month-old rats. In 24-month-old rats initial liver injury at 6 h was similar to the 3- and 14-month-old rats and thereafter did not develop to the level of the other two age groups, recovering from injury by 96 h as in the 14-month-old rats. Neither hepatomicrosomal CYP2E1 protein nor the associated p-nitrophenol hydroxylase activity or covalent binding of 14CCl4-derived radiolabel to liver tissue differed between the age groups or diet regimens 2 h after the administration of 14CCl4. Compensatory liver tissue repair (3H-T, PCNA) was prompt and robust soon after CCl4 liver injury in the 14- and 24-month-old rats. In stark contrast, in the 3-month-old rats it failed allowing unabated progression of liver injury. These findings suggest that stimulation of early onset and robust liver tissue repair rescue the 14- and 24-month-old F344 rats from the lethal effect of the CD+CCl4 combination.
authors.affiliation: Department of Toxicology, Sugar Hall #306, School of Pharmacy, College of Health Sciences, The University of Louisiana at Monroe, 700 University Avenue, Monroe, LA 71209, USA.
authors.forename: B
authors.initials: B
authors.lastname: Murali
authors.forename: M C
authors.initials: MC
authors.lastname: Korrapati
authors.forename: Alan
authors.initials: A
authors.lastname: Warbritton
authors.forename: John R
authors.initials: JR
authors.lastname: Latendresse
authors.forename: Harihara M
authors.initials: HM
authors.lastname: Mehendale
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D002251:Carbon Tetrachloride / Q000633:toxicity*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D056486:Chemical and Drug Induced Liver Injury / Q000473:pathology; D007631:Chlordecone / Q000633:toxicity*; D004247:DNA / Q000378:metabolism; D004357:Drug Synergism; D004798:Enzymes / Q000097:blood; D007306:Insecticides / Q000633:toxicity*; D008099:Liver / Q000473:pathology / Q000502:physiology; D008111:Liver Function Tests; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D013936:Thymidine / Q000378:metabolism
chemical_list: D004798:Enzymes; D007306:Insecticides; D004247:DNA; D002251:Carbon Tetrachloride; D007631:Chlordecone; D013936:Thymidine