Double-tracer autoradiographic study of protein synthesis and glucose consumption in rats with focal cerebral ischemia

A double-tracer autoradiographic method for simultaneous measurement of reg ional glucose utilization (rCMR(glc)) and regional protein synthesis (FS) i n consecutive brain sections is described and applied to study the metaboli sm of the ischemic penumbra 2 h after occlusion of the middle cerebral arte ry (MCAO) in rats. In halothane anesthesia, the left middle cerebral artery was permanently occluded. Two hours after MCAO an i.v. bolus injection of C-14-deoxyglucose and H-3-leucine was given and circulated for 45 min. Two sets of brain sections were processed for quantitative autoradiography. Nei ghboring brain sections exposed an X-ray film (H-3-insensitive), and a H-3- sensitive for determination of rCMR(glc) and PS, respectively. Sections for PS determination were washed in trichloroacetic acid (TCA) prior to film e xposure in order to remove C-14-deoxyglucose and unincorporated H-3-leucine . Regional rates of PS and glucose utilization were measured by densitometr ic image analysis. Normal rates of metabolism were defined as mean +/- 2 SD of values in the non-ischemic cortex. The volumes of ischemic cortex displ aying normal rates of PS and glucose utilization, respectively, were measur ed. The cortical volume with normal PS was significantly less than that of normal rCMR(glc): 142 (127-147) mm(3) vs. 203 (184-206) mm(3). Treatment wi th the glutamate antagonists MK-801 (1 mg kg(-1)) and NBQX (30 mg kg(-1) x 2) did not significantly change this, although MK-801 tended to reduce the size of the metabolic penumbra calculated as the difference between ischemi c cortex with reduced PS and ischemic cortex with reduced rCMR(glc).