Effects of decapitation-stress on the phosphorylation of cortical membrane proteins

The endogenous phosphorylation of membrane-bound proteins was studied in preparations from the cerebral cortex of rats sacrificed by immersion in liquid nitrogen or by decapitation. Compared to quick-frozen rats, samples from decapitated animals demonstrated a two-fold increase in ^{3 2}P-phosphate incorporation into specific protein bands with apparent molecular weights of 56K, and 52K (designated E₁ and E₂) and a decreased incorporation into a phosphoprotein of 47K (designated F). The phosphorylation of two proteins (78K and 34K) in membranes from decapitated rats was found to be highly stimulated by exogenously added cyclic AMP. On the other hand, the phosphorylation of specific protein bands in preparations from quick frozen rats was minimally affected by addition of cyclic AMP. The results indicate that conditions which lead to increases in cyclic AMP levels in the brain in situ induce specific changes in phosphorylative activity, and these can be detected by assaying isolated membrane fragments in vitro.