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  • 1
    ISSN: 1432-0738
    Keywords: CCl4 ; Chlordecone ; Potentiated hepatotoxicity ; Suppressed liver regeneration ; Partial hepatectomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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 μl/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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0738
    Keywords: Chlordecone ; Carbon tetrachloride ; Partial hepatectomy ; 3H-thymidine incorporation ; DNA ; Potentiation ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous histomorphometric studies led us to hypothesize that suppression of hepatocellular regeneration and the repair of the hepatolobular architecture was involved besides bioactivation phenomenon in the progressive and irreversible phase of toxicity resulting from CD + CCl4 interaction. We have recently observed significant protection from CD potentiated CCl4 toxicity in animals which are stimulated for active hepatocellular regeneration. The present work is an extension of our earlier histomorphometric investigation, taking 3H-thymidine (3H-T) incorporation as a biochemical parameter to assess hepatocellular regeneration followed by autoradiographic analysis of liver sections in normal (N) or chlordecone (CD) treated (10 ppm in diet for 15 days) male rats undergoing sham (SH) or partial hepatectomies (PH). Initial experiments established that in normal (N) rats, greatest 3H-T incorporation into hepatocellular nuclear DNA occurs at 2 days post-PH which returns to basal levels by 7 days. CD treatment alone did not change this phenomenon. 3H-T incorporation into nuclear DNA and the percentage of labelled cells as evidenced by autoradiography of liver sections were significantly elevated in N rats at 1–2 h after CCl4 (100 μl/kg) administration and returned to basal level by 6 h. Serum enzymes (AST and ALT) in N rats undergoing SH and PH were not altered, but were significantly elevated in CD rats following CCl4 (100 μl/kg) administration. CCl4-induced serum enzyme elevations were significantly lower in 2 days post-PH (PH2) rats when compared to SH rats or 7 days post-PH (PH7) rats maintained on CD diet, indicating that CD potentiated CCl4 hepatotoxicity is significantly reduced in livers stimulated for regenerative activity by PH. CCl4 decreased the DNA levels significantly in SH2, SH7 and PH7 rats, but not in PH2 rats receiving CD diet. 3H-T incorporation, percentage of labelled cells and number of grains per cell were significantly decreased at 2 h in PH2 rats receiving the CD + CCl4 combination treatment, reflecting the suppression of cell proliferation after CCl4 administration to CD fed rats. These results indicate that PH affords protection against CD + CCl4 interaction. The protection against hepatotoxic and lethal effects of CD + CCl4 combination by previously stimulated hepatocellular regeneration might be explained by two consequences of stimulated cell division. First, the hepatocellular architecture is renovated by the newly divided cells. Second, by virtue of the well known resistance of the newly divided cells, the progressive phase of toxicity is inhibited. These findings are supportive of our hypothesis that suppression of hepatocellular regeneration besides bioactivation phenomenon is involved in CD + CCl4 toxicity.
    Type of Medium: Electronic Resource
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