Blood was centrifuged at 3000 3 g for 20 min at 4C to obtain
plasma and erythrocytes. Erythrocytes were washed twice with 5 mL
cold EDTA solution (5 mmol/L), mixed gently, centrifuged at 3000 3 g
for 20 min at 4C, and stored at 280C for at least 15 min. After
thawing, erythrocyte lysate was obtained and 300 mL was deproteinized
by adding an equal volume of 6% sulfosalicylic acid. Plasma (1 mL) was
deproteinized by the addition of 100 mL 30% sulfosalicylic acid. After
centrifugation (30003 g, 20min, 4C), 20 mL of the supernatant obtained
from plasma and erythrocytes was removed and stored at 280C until
analysis (see below).