bled for collecting blood samples via anterior vena cava puncture into
K3EDTA vacuum tubes or clot activator vacuum tubes (Becton
Dickinson Vacutainer Systems, Franklin Lakes, NJ, USA). The blood samples
were collected during 11:00 to 12:00 h in order to exclude the circadiurnal
fluctuations in hormone concentrations and stored at −4°C.
Blood samples from clot activator vacuum tubes were centrifuged
(3,000×g) for 15 min at 4°C to obtain serum samples and then
stored at −20°C until analysis. The concentrations of blood
urea nitrogen (BUN) and creatinine in serum were analyzed by an automatic
biochemical blood analyzer (HITACHI 747, Hitachi, Tokyo, Japan). The
concentrations of immunoglobulin G (IgG), immunoglobulin A (IgA), and
immunoglobulin M (IgM) in serum were determined using an enzyme-linked
immunosorbent assay kit (ELISA Starter Accessory Package, Bethyl
Laboratories, Montgomery, TX, USA). In addition, whole blood samples from
the K3EDTA vacuum tube were analyzed for white blood cell (WBC),
red blood cell (RBC), and lymphocyte concentrations using an automatic blood
analyzer (ADVIA 120, Bayer, Tarrytown, NY, USA).