Environmental factors like temperature, humidity, noise and light could affect laboratory animals and have an influence on toxicity study results. This study was performed to investigate how a disturbed light-dark cycle could affect CCl
4-induced toxicity in F344/N female rats.
CCl
4, a well-known liver toxicant, induced liver toxicity in F344/N female rats as demonstrated by histopathologic findings like fatty changes and necrosis, and elevation of ALT and AST. However, CCl
4-induced ballooning degeneration and necrosis in rat liver of a normal light-dark cycle was changed by a disturbed light-dark cycle. High-dose CCl
4 treatment in the disturbed light-dark cycle group had a significant decrease of both mild and moderate ballooning degeneration than in the normal light-dark cycle group. Both low and high doses of CCl
4 in disturbed light-dark cycle group showed a significant decrease of CCl
4-induced necrosis than in the normal light-dark cycle group. A disturbed light-dark cycle altered hormone levels such as corticosterone and melatonin. It increased corticosterone level and decreased melatonin level. The disturbed light-dark cycle group and the normal light-dark cycle group showed similar increase in body weight and food intake but water intake decreased in the disturbed group.
Our results demonstrate that disturbed lighting in a laboratory toxicity experiment causes physiological changes like hormones and body weight, and thus, can affect the results of a toxicity test.
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