Human serum was obtained from 26 healthy Japanese subjects. This study was approved by the Ethics Committee of the Faculty of Pharmaceutical Science, Toho University (No. 24-6 and 26-1).
Age- and sex-matched healthy volunteers (11 men, ages 26.8±6.70 years; 15 women, 26.4±7.60 years [mean±SD]) were recruited after providing written informed consent. Approximately 5.0mL blood was drawn from the arm vein of each volunteer into VENOJECT II tubes (VP-AS109 K; Terumo, Tokyo, Japan) between 11:00 and 13:00 before consuming lunch. Blood was transferred to a
shaded container and allowed to stand for 30 min at room temperature. Samples were then centrifuged at 1200×g for 15 min, and the isolated sera were stored at –80 ◦C until analysis.