Paraquat and diquat facilitate formation of superoxide anion in biological systems, and lipid peroxidation has been postulated to be their mechanism of toxicity. Paraquat has been shown to be more toxic to selenium-deficient mice than to controls, presumably as the result of decreased activity of the selenoenzyme glutathione peroxidase. The present study was designed to measure lipid peroxidation and to assess toxicity in control and selenium-deficient rats given paraquat and diquat. Lipid peroxidation was measured by determining ethane production rates of intact animals; toxicity was assessed by survival and by histological and serum enzyme evidence of liver and kidney necrosis. Paraquat and diquat were both much more toxic to selenium-deficient rats than to control rats. Diquat (19.5 μmol/kg) caused rapid and massive liver and kidney necrosis and very high ethane production rates in selenium-deficient rats. The effect of paraquat (78 μmol/kg) was similar to that of diquat but was not as severe. Acutely lethal doses of paraquat (390 μmol/kg) and diquat (230 μmol/kg) in control rats caused very little ethane production and no evidence of liver necrosis. These findings suggest that paraquat and diquat exert their acute toxicity largely through lipid peroxidation in selenium-deficient rats. Selenium deficiency had no effect on superoxide dismutase activity in erythrocytes or in 105,000 g supernate of liver or kidney. Glutathione peroxidase, which represents the only well-characterized biochemical function of selenium in animals, was dissociated from the protective effect of selenium against diquat-induced lipid peroxidation and toxicity by a time-course study in which selenium-deficient rats were injected with 50 μg of selenium and later given diquat (19.5 μmol/kg). Within 10 h, the selenium injection provided significant protection against diquat-induced lipid peroxidation and mortality even though this treatment resulted in no rise in glutathione peroxidase activity of liver, kidney, lung, or plasma at 10 h. This suggests that a selenium-dependent factor in addition to glutathione peroxidase exists that protects against lipid peroxidation.
Raymond F. Burk, Richard A. Lawrence, James M. Lane
Usage data is cumulative from April 2023 through April 2024.
Usage | JCI | PMC |
---|---|---|
Text version | 171 | 0 |
54 | 60 | |
Figure | 0 | 2 |
Scanned page | 61 | 3 |
Citation downloads | 8 | 0 |
Totals | 294 | 65 |
Total Views | 359 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.