Changes in tissue glutathione antioxidant system in streptozotocin-induced diabetic rats for a period of 15 weeks were examined. Total glutathione level was significantly increased in kidney tissue, but were slightly decreased and increased in liver and heart tissues, respectively. The small changes in total glutathione level in the liver and heart, though not statistically significant, were associated with reciprocal alterations in the activity of gamma-glutamylcysteine synthetase (GCS). While the GCS activity was not changed in kidney tissue, the activity of gamma-glutathione peroxidase was significantly increased in kidney tissue. Insulin treatment could completely or partly normalize almost all of these changes induced by diabetes. However, the decrease in hepatic glutathione S-transferases activity in diabetic rats was not reversed by the insulin treatment. The ensemble of results suggests that the diabetes-induced alterations in tissue glutathione antioxidant system may possibly reflect an inter-organ antioxidant response to a generalized increase in tissue oxidative stress associated with diabetes.
ABSTRACT-Exposure of liver homogenates to an in vitro tert-butyl hydroperoxide challenge can be used as a means for measuring the reduced glutathione regeneration capacity (GRC) of hepatic tissues. Pretreatment of rats with a lignan-enriched extract of Fructus Schisandrae (FS) caused a moderate enhancement of hepatic GRC in control rats, but the GRC enhancing effect of FS pretreatment on hepatic tissues was greatly exaggerated after CC14 challenge. This in vitro bioassay can be used for investigating the hepatic GRC promoting action of orally active agents.
Treatment of rats with a lignan-enriched extract of the fruit of Schisandra chinensis could enhance hepatic antioxidant/detoxification system, as indicated by increases in hepatic reduced glutathione (GSH) level as well as hepatic glutathione reductase and glutathione S-transferase activities. The hepatoprotective action was evident after aflatoxin beta 1 or cadmium chloride (Cd) challenge. Schisandra chinensis pretreatment protected against aflatoxin B1-or Cd-induced hepatocellular damage in rats. However, pretreating rats with alpha-tocopherol acetate (vitamin E) did not protect against hepatic damage induced by both toxins. Results from the present as well as our previous studies demonstrate that the hepatoprotection afforded by Schisandra chinensis pretreatment is not hepatotoxin specific. Schisandra chinensis seems to be more effective than vitamin E in protecting against aflatoxin B1 and Cd toxicity. The mechanism of hepatoprotection afforded by Schisandra chinensis pretreatment may involve facilitation of both antioxidant and detoxification processes in the liver.
Sheng-Mai-San (SMS), a traditional Chinese formulation used for the treatment of coronary heart disease, is comprised of Radix Ginseng, Fructus Schisandrae and Radix Ophiopogonis. Pretreatment with a lignan-enriched SMS (17 g/kg/day x 3, p.o.) was found effective in protection against isoproterenol-induced myocardial injury in rats, and in ischemia-reperfusion injury in isolated perfused hearts prepared from pretreated animals. Results obtained from pretreatment studies using extracts prepared by mixing various combinations of the three component herbs indicate that the major myocardial protective component in SMS is the lignan-enriched extract of Fructus Schisandrae.
Effects of Schisandrin B (Sch B) and alpha-tocopherol (alpha-TOC) on ferric chloride (Fe3+) induced oxidation of erythrocyte membrane lipids in vitro and carbon tetrachloride (CCl4) induced lipid peroxidation in vivo were examined. While alpha-TOC could produce prooxidant and antioxidant effect on Fe(3+)-induced lipid peroxidation, Sch B only inhibited the peroxidation reaction. Pretreatment with alpha-TOC (3 mmol/kg/day x 3) did not protect against CCl4-induced lipid peroxidation and hepatocellular damage in mice, whereas Sch B pretreatment (0.3 mmol/3.0 mmol/kg/day x 3) produced a dose-dependent protective effect on the CCl4-induced hepatotoxicity. The ensemble of results suggests that the ability of Sch B to inhibit lipid peroxidation, while in the absence of pro-oxidant activity, may at least in part contribute to its hepatoprotective action.
We have demonstrated that pretreatment with a lignan‐enriched extract of Fructus schisandrae (FS) protected against physical exercise‐induced muscle damage in rats. The muscle protection afforded by FS pretreatment was associated with a significant enhancement in hepatic antioxidant status, as assessed by hepatic glutathione (GSH) and malondialdehyde (MDA) levels. Pretreating rats with α‐tocopherol acetate, though decreasing the MDA level in skeletal muscle, did not protect against exercise‐induced muscle damage or improve hepatic antioxidant status in exercised rats. The results indicate that the protective effect of FS pretreatment on physical exercise‐induced muscle damage may result from the enhancement of hepatic GSH status, thereby providing sufficient GSH for effective antioxidant protection of skeletal muscle during exercise.
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