Mechanisms of Ischemic Cell Swelling in the Brain

Abstract

Swelling of nervous and glial elements is a predominant feature of ischemic brain edema [2]. The critical threshold of cerebral blood flow depression causing ischemic water uptake into the brain is approximately 40% of normal [18]. Major disturbances of the blood-brain barrier function do not seem to be involved at that stage. Based on the classical notion of the double Donnan equilibrium, it is currently held that cell swelling under these circumstances is the result of a failing energy metabolism no longer capable of fuelling active pumping for compensation of the continuing cellular influx of Na⁺, Cl⁻, and water [16]. Although cell volume regulation seems to depend on a functional energy metabolism (cf. Table 1), it remains questionable whether the concept of the Donnan equilibrium suffices to explain the rapid onset of cell swelling upon interruption or marked depression of blood flow to cerebral tissue. The mechanisms involved in ischemic cell swelling appear far more complex on a molecular level.