Changes in the incorporation of 14C-amino acids into proteins in vitro were followed under conditions of ischemia induced by abdominal aorta ligature and subsequent recirculation in dogs. Cell saps isolated from L-S spinal cord, spinal ganglia, the sciatic nerve and medulla oblongata were added to the incorporation mixture composed of ribosomes and an enzymatic system from intact brains. Cytosols isolated from ischemic animals affected the rate of in vitro protein synthesis moderately, while repeated ischemia caused a profound decrease in the incorporation of amino acids into proteins. Cytosols from L-S spinal cord and especially from spinal ganglia after three days of recirculation substantially enhanced incorporation thus indicating a massive response of these tissues to ischemic injury. Cell saps from the medulla oblongata increased amino acid incorporation into proteins in vitro in all experimental groups.