Regional Flow-Metabolism Couple following Middle Cerebral Artery Occlusion in Cats

The regional flow-metabolism couple was studied during the recovery period after 1 h of left middle cerebral artery (MCA) occlusion in cats. Local CBF (LCBF) was assessed at the end of ischemia as well as at the end of 4 h of recirculation by the microsphere technique. Local CMRgl (LCMRgl) was measured at the end of the recirculation period with [¹⁴C]2-deoxyglucose. Histology was evaluated by light microscopy from coronal brain blocks adjacent to those used for the determination of LCBF and LCMRgl. When LCBF in the central and peripheral MCA territories during the recovery period was between 40 and 115% of the value in sham occlusion studies, LCMRgl was greater than the control level found in the sham studies, and was accompanied by slight histological damage. This finding suggests that anaerobic glycolysis may persist after transient ischemia in spite of the recovery of LCBF to a level that is normally greater than the threshold for the activation of anaerobic glycolysis (<40% of the control). Persistent anaerobic glycolysis in the reperfusion period following an ischemic insult may be a sign of early tissue damage. Some of the regions in the peripheral MCA territory with LCBF between 40 and 110% of the levels during the recovery period in the sham studies showed a mild to moderate depression in LCMRgl so that the flow-metabolism ratio remained normal. These regions did not exhibit histological damage. This possible protective mechanism of the tissue in response to ischemia is discussed from the standpoint of the relationship between flow and metabolism.