Protection of chlordecone-potentiated carbon tetrachloride hepatotoxicity and lethality by partial hepatectomy

Chlordecone (CD) pretreatment is known to markedly potentiate CCl₄ hepatotoxicity. Previous studies have shown that prior exposure to CD obtunds the increased hepatocellular regeneration and repair observed in non-treated rats challenged with a single, low dose of CCl₄. These observations allowed us to hypothesize that suppression of hepatic regeneration and tissue repair by CD + CCl₄ combination treatment might be involved in this interaction. To test this hypothesis, CCl₄ hepatotoxicity was evaluated in actively regenerating livers using CD-treated (10 ppm in the diet for 15 days), surgically partially hepatectomized (PH) male Sprague-Dawley rats. Rats undergoing no surgical manipulation (CTRL) and sham operation (SH) were included as appropriate controls. Surgical manipulations were conducted on day 15 of the dietary protocol. Based on liver-to-body weight ratios (LW/BW), mitotic indices, hepatic cytochrome P-450 content, and hepatic glutathione (GSH and GSSG) levels, PH-induced hepatocellular regeneration was not affected by pretreatment with CD. Thus, the PH model was considered valid for assessing the effects of CD + CCl₄ combination treatment. CCl₄ (100 l/kg; i.p.) was administered 1, 2, 4 or 7 days after the surgical manipulations. Hepatotoxicity was assessed 24 h later by measuring LW/BW and serum enzymes (SGPT, SGOT and ICD) in all four groups. Hepatic histopathological, histomorphometric and lethal effects were assessed in animals receiving CCl₄ 1 or 7 days after the surgical manipulations. CCl₄-induced increases in LW/BW were observed in CD + PH rats receiving CCl₄ 4 or 7 days post-PH, but not in the 1 or 2 day post-PH groups in which the hepatocellular regeneration was maximal. CCl₄-induced serum enzyme elevations were significantly less in the CD + PH rats as compared to CD + SH. This decrease in the serum enzyme elevations was most prominent in the 1 day post-PH group, where the hepatocellular mitotic activity was most pronounced. CCl₄ lethality, assessed in the 1 day post-surgical manipulation group, was also decreased in the CD + PH rats in comparison to CD + SH rats. Such a protection was not observed in rats receiving CCl₄ 7 days post-PH. These data are consistent with and are supportive of the hypothesis that a suppression of otherwise normally stimulated hepatocellular regeneration following low-dose CCl₄ administration is involved in the marked amplification of CCl₄ toxicity by CD.Abbreviations CD chlordecone - GSH reduced glutathione - GSSG oxidized glutathione - PH partial hepatectomy - SH shamhepatectomy - CTRL control, not surgically manipulated - N normal diet - LW/BW liver weight-to-body weight ratio - SGPT serum glutamic; pyruvic transaminase - SGOT serum glutamic oxaloacetic transaminase - ICD isocitrate dehydrogenase These studies were made possible by a grant from the US Environmental Protection Agency R-811072A preliminary report of these findings was presented at the 70th Annual Meetings of the Federation of American Societies for Experimental Biology at St. Louis, MO (Fed Proc 45: 1051, 1986)A. N. Bell is a Predoctoral Toxicology Trainee and Robert A. Young is a Postdoctoral Trainee supported by Toxicology Training grant from National Institute of Environmental Health Science ES-07045