Mechanism of protein synthesis inhibition in CNS during postischaemic reperfusion

We have used brain (dog, rat) and spinal cord (dog, rabbit) cell-free systems to study early postischaemic inhibition of protein synthesis. Ischaemia alone produced a relatively small decrease in activity of all subcellular systems used. When 15 min of normoxic reperfusion was used, more than 30% decrease (p less than 0.01) in [14C]-leucine incorporation was detected. A translational inhibitor that appeared in the postribosomal supernatant fraction at the early stage of reperfusion reduced translational capacity of an initiating cell-free system. It also phosphorylated the small (38 kDa) subunit of eukaryotic initiation factor 2 (eIF-2) in vitro. Effect of the inhibitor can be reversed by addition of partially purified intact eIF-2 and/or high concentration (2 mmol/l) of GTP. A prevention of postischaemic free oxygen radical formation by the reoxygenation with hypoxaemic blood, containing 37.5 mm Hg O2 at 0-5 min and 56 mm Hg O2 at 6-10 min of recirculation, that was followed by 5 min of normoxic reperfusion, resulted in a significant increase (p less than 0.02) of polypeptide chain synthesis in vitro when compared with normoxic reperfusion.