脳循環代謝よりみた脳虚血—脳組織pH Homeostasisを中心に

Cerebral circulation and metabolism in cerebral ischemia: With particular reference to pH homeostasis.

　脳虚血のさいの脳循環代謝動態については，今までにも多くの優れた解説^1〜8）が発表されている。本稿では，あえてその繰り返しは避け，今回の特集の趣旨に添い，古くて新しい問題の一つである虚血時のacid-base balanceにつき，とくにH^＋（proton）動態の面より解析し，合わせて臨床的にも問題となるhyperglycemiaの脳虚血における功罪につき解説を加えてみた。

　The mechanism of pH homeostasis in braintissue and its derangement in brain ischemia were reviewed. The four major mechanisms contribute to the maintenance of pH in the normal brain : 1) production and consumption of H⁺ by brain metabolism, 2) physicochemical buffering, 3) transmembrane trantport of H⁺ and its equivalent, 4) compensatory adaptation of circulatory factors.

　In brain ischemia, activation of anaerobic glycolysis together with hydrolysis of its product (ATP) is a major factor which produces H⁺ depending on intracellular pH. Consumption of H⁺ by metabolism of creatine phosphate and glycogen, or oxidation of lactate is almost negligible under ischemic condition.