局所脳虚血におけるグルコース利用率の可逆性

REVERSIBILITY OF LOCAL CEREBRAL GLUCOSE UTILIZATION AFTER TRANSIENT FOCAL ISCHEMIA

　抄録　ラット局所脳虚血モデルにて中大脳動脈（MCA）閉塞および血流再開後の局所脳グルコース利用率（LCGU）と局所脳血流量（LCBF）の変化を定量的autoradiography法を用いて検討した。2時間および3時間のMCA閉塞で脳虚血の中心であるsensorimotorcortexではLCBFは70％の低下を示し，2時間のMCA閉塞後，血流再開1時間後には，LCBFは改善の傾向を示し30％の低下にとどまった。LCGUは2時間のMCA閉塞にて，radioactivityの低い虚血の中心とその周囲にradiQactivityの高い部分が存在するabnormal patternを示し，3時間のMCA閉塞ではさらにその異常は増強した。2時間のMCA閉塞後，血流再開にてLCGUはほぼnormal patternとなった。脳虚血の可逆性は虚血の程度と虚血時間などによって決定されると考えられる。虚血の強いglobal ischemiaと側副血行などの存在するfocal is—chemiaとは区別する必要がある。今回用いた比較的軽度のfocalischemiaでは，2時間の虚血において，LCBFと同様にLCGUにおいても可逆性が認められたと考えられる。

Although changes in local cerebral blood flow and glucose metabolism during and following transint "global" ischemia have been discussed, no reports for these changes in transient "focal" ischemia have been made. In the present report we studied reversibility of cerebral blood flow and glucose metabolism after transient "focal" ischemia.

Focal ischmia was induced in rat by clipping a left middle cerebral artery by Zen's clip. Local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCGU) were measured by quantitative autoradiography using ¹⁴C-iodoanti-pyrine and ¹⁴C-deoxyglucose, respectively.

At 2 and 3 hours after clipping, 70% reduction of LCBF was found in the left sensorimotor cortex. At one hour after restoration of blood flow from 2 hours of occlusion LCBF recovered to 70% of controls. At 2 and 3 hours after clip-ping, LCGU was low in the territories of the left MCA, which were surrounded by zones of high LCGU. Low LCGU may represent a depressed glucose metabolism and high LCGU, anaerobic glycolysis. The abnormal pattern of LCGU seen at 2 hours after occlusion was clearly improved by restoration of blood flow.

The results indicate that glucose metabolism might be reversible in the moderate degree of focal cerebral ischemia, and early restoration of blood flow may be beneficial for glucose meta-bolism.