Experimental stroke in gerbils: effect on translation and transcription

The effect of cerebral ischemia on polypeptide synthesis with isolated microsomes and DNA-dependent RNA polymerase activity with isolated nuclei was investigated by occlusion of right common carotid artery of gerbils. There was a prompt decline of microsomal polypeptide synthesis already at 30 min after occlusion of the artery, and at 4--5 h the specific radioactivity (dpm per microgram protein) was 50% of the control value. At 24 h, when the animals were only slightly responsive to external stimuli, the specific radioactivity of ischemic brain was only 20% of the control value. DNA-dependent RNA polymerase activity was unaffected for 1 h, and clear suppression did not appear until 3 h after occlusion. However, the extent of suppression was similar between polypeptide synthesis and RNA polymerase activity beyond 3 h after occlusion. Although more selective vulnerability of polypeptide synthesis thus exists in cerebral ischemia, the difference between two biochemical processes was not as striking as seen in cerebral anoxia. Focal progression of cerebral ischemia to diffuse infarction in gerbils was suggested as a possible explanation for the disparity in comparison to the diffuse effect in cerebral anoxia along with the difference in the magnitude of acidosis and depletion of energy reserve.