Detection of GIRK subunits in platelets by Western blotting. Washed and aspirin-treated human platelets were lysed with (3×) sample buffer, and 10 μLof protein lysate was loaded onto a 10% Tris-glycine gel. Western blotting was performed using specific antibodies against GIRK1, GIRK2, and GIRK4 (A) and in the presence of blocking peptides as described in “Materials and methods” (B). The molecular weights are indicated in each of the blots. The predominant GIRK1 band was noticed at approximately 55 kDa. GIRK2 and GIRK4 both were detected at 47.5 kDa molecular weight range. The blot was probed with antibodies against PKC-δ to ensure equal loading of lanes with protein.