Fig. 4. Effect of cardiopulmonary bypass (CPB) on Gsα, Giα, and GRK2 in mononuclear cells (n = 3). The Gsα, and Giαimmunoreactivity was determined in mononuclear cell membrane, and GRK2 immunoreactivity was measured in mononuclear cell cytosol in PRE, POST, and POD1 samples from three different patients. The G protein immunoblot utilized 20 μg of membrane protein, and the GRK2 immunoblot utilized 30 μg of cytosolic protein from each sample. The consistent decrease in GRK2 after CPB does not occur in G proteins after CPB, demonstrating that the decrease in GRK2 is not due to a decrease in all proteins associated with the GPCR signaling network. PRE = before surgery; POST = 2 h after completion of CPB; POD1 = 24 h after completion of CPB.