α-Tocopherol protects against α-naphthylisothiocyanate-induced hepatotoxicity in rats less effectively than melatonin

Abstract The protective effect of α-tocopherol (α-Toc), which exerts antioxidant and anti-inflammatory actions, against α-naphthylisothiocyanate (ANIT)-induced hepatotoxicity in rats was compared with that of melatonin because orally administered melatonin is known to protect against ANIT-induced hepatotoxicity in rats through its antioxidant and anti-inflammatory actions. Rats intoxicated once with ANIT (75 mg/kg, intraperitoneal (i.p.)) showed liver cell damage and biliary cell damage with cholestasis at 24 h, but not 12 h, after intoxication. ANIT-intoxicated rats received α-Toc (100 or 250 mg/kg) or melatonin (100 mg/kg) orally at 12 h after intoxication. The α-Toc administration protected against liver cell damage in ANIT-intoxicated rats, while the melatonin administration protected against both liver cell damage and biliary cell damage with cholestasis. ANIT-intoxicated rats had increased hepatic lipid peroxide concentration and myeloperoxidase activity at 12 and 24 h after intoxication. ANIT-intoxicated rats also had increased serum α-Toc and non-esterified fatty acid (NEFA) concentrations at 12 and 24 h after intoxication and increased serum triglyceride and total cholesterol concentrations at 24 h. The administration of α-Toc to ANIT-intoxicated rats increased the hepatic α-Toc concentration with further increase in the serum α-Toc concentration and attenuated the increased hepatic lipid peroxide concentration and myeloperoxidase activity and serum NEFA concentration at 24 h after intoxication. The melatonin administration did not affect the hepatic α-Toc concentration but attenuated the increased hepatic lipid peroxide concentration and myeloperoxidase activity and serum α-Toc, NEFA, triglyceride, and total cholesterol concentrations at 24 h after ANIT intoxication. These results indicate that orally administered α-Toc protects against ANIT-induced hepatotoxicity in rats possibly through its antioxidant and anti-inflammatory actions less effectively than orally administered melatonin.