Abstract: AIM: To establish a method to determine the concentrations of L-carnitine (LC) and its active metabolites in plasma and hepatic tissue of rabbit by precolumn derivatization HPLC. It was detected the content that the LC and its active metabolites of endogenous and after a single dose by intragastrical administration. METHODS: A single dose of 1 mL/kg that LC was taken orally to New Zealand rabbits with big ears. The plasma and hepatic tissue samples were taken before and after administration respectively. The concentrations of LC and its active metabolites in plasma and hepatic tissues were measured using pre-column derivatization HPLC. RESULTS: The method showed good linear response over the selective concentration range of 2-200, 0.2-40 and 0.1-8 μmol/L for LC, acetyl-L-carnitine (ALC) and propionyl-L-carnitine (PLC), respectively. The intra-day and inter-day validations were less than 4.12% for three agents; The average methods recoveries of assay were 80%-95%. The plasma concentrations of LC, ALC and PLC in blank rabbits were 15.78, 2.15 and 0.47 μmol/L,respectively, and their concentrations in hepatic tissue were 24.83, 4.61, and 2.08 μmol/g,respectively. After administration for 7 h to rabbits, the concentrations of LC and its active metabolites have a significant change in plasma and hepatic tissue. CONCLUSION: This method is simple, reliable and accurate. These results show that in the absorption process of LC in vivo, LC is acetylated and propionylated, and transformed to active metabolites ALC and PLC. In hepatic tissue, concentrations of LC and its active metabolites are significantly higher than in plasma, indicating that LC and its active metabolites distributied are transfer from plasma to hepatic tissue quickly.

Key words: L-carnitine, Acetyl-L-carnitine, Propionyl-L-carnitine, HPLC, Rabbit