Role of antioxidant enzyme defence in sparing rat hepatocytes from toxicity of ricin at low dose.

Ricin, a glycoprotein from castor oil seeds, is specifically toxic to Kupffer cells and at low doses it leaves parenchymal cells comparatively unaffected. At a dose of approximately 1.5 microgram/100 g body weight, ricin significantly increases the hepatic antioxidant enzyme system in rats within 24 hr. Superoxide dismutase, catalase and glutathione peroxidase show an increase in liver tissue levels of 19-24%. However, hepatic lipid peroxidation is elevated by about 34% and non-protein sulphydryl is reduced by 26%. The enhanced levels of antioxidant enzymes appear to protect the hepatocytes from the toxin. The observed elevation of hepatic thiobarbituric acid-reactive substances appears to originate mainly from the damaged Kupffer cells.