Melatonin attenuates disruption of serum cholesterol status in rats with a single α-naphthylisothiocyanate treatment

: The present study was performed to examine whether melatonin attenuates disruption of serum cholesterol status in rats treated once with α‐naphthylisothiocyanate (ANIT). In the serum of rats treated with ANIT (75 mg/kg, i.p.), increases in total cholesterol, free cholesterol (F‐Chol), low‐density lipoprotein cholesterol, very low‐density lipoprotein cholesterol, and total bile acid concentrations and a decrease in the ratio of esterified cholesterol concentration to F‐Chol concentration occurred 24 hr, but not 12 hr, after the treatment. In the liver of ANIT‐treated rats, a decrease in cholesterol concentration and an increase in total bile acid concentration occurred 24 hr, after 12 hr, after the treatment. When melatonin (10 or 100 mg/kg, p.o.) was administered to ANIT‐treated rats at 12 hr after the treatment, all these changes found in the serum and liver at 24 hr after the treatment were significantly attenuated at the higher dose. Melatonin (100 mg/kg) administered to ANIT‐untreated rats in the same manner increased the serum F‐Chol and high‐density lipoprotein cholesterol concentrations significantly. These results indicate that orally administered melatonin attenuates the disruption of serum cholesterol status in rats treated once with ANIT possibly by maintaining cholesterol metabolism and transport in the serum and liver.