2.9. Western blotting
The tissue homogenates were mixed with 5× sample buffer (8% SDS; 0.04%
Coomassie blue R-250; 40% glycerol; 200 mM Tris, pH 6.8 and 10% 2-mercaptoethanol)
and boiled for 10 min. Samples were electrophoresed in a 10% SDS-PAGE minigel and
then transferred onto polyvinylidenedifluoride membranes (PVDF; Millipore Corp.,
Bedford, MA, USA) with transfer buffer (48 mM Tris; 39 mM glycine; 0.0037% SDS and
20% methanol) at 350 mA for 60 min. The membranes were blocked with 5% nonfat
milk in PBS solution containing 0.1% Tween-20 (PBST) for 1 h. The membrane was
immunoblotted, respectively, with primary antibodies of rabbit anti-rat Nrf2, anti-Aβ
and anti-rat mitogen-activated protein kinase (MAPK) family in PBST solution
containing 5% bovine serum albumin at 4°C overnight. After consecutive 30-min
PBST washes, the membrane was incubated with horseradish peroxidase-labeled
secondary antibody for 60 min at room temperature and then washed with PBST for 30
min. The final detection was performed using an enhanced chemiluminescence (ECL™
kit) Western blotting reagents (Amersham Pharmacia Biotech, NJ, USA)