American journal of physiology. Cell physiology
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Am. J. Physiol., Cell Physiol. · Jan 2008
Hypoxia effects on cell volume and ion uptake of cerebral microvascular endothelial cells.
Increased transport of Na across an intact blood-brain barrier (BBB) contributes to cerebral edema formation in ischemic stroke. Our previous studies have shown that ischemic factors stimulate activity of a luminal BBB Na-K-Cl cotransporter, and we have hypothesized that during ischemia, the cotransporter together with the abluminal Na/K pump mediates increased transport of Na from blood into the brain. However, it is possible that elevated Na-K-Cl cotransporter activity could also cause cell swelling if it outpaces ion efflux pathways. ⋯ By ion chromatography methods, we also found that a 30-min exposure to 7.5% O(2) caused an increase in bumetanide-sensitive net Na uptake by the cells without increasing cell Na content. CMEC Na content was significantly increased, however, following 3 or more hours of exposure to 7.5% O(2). These findings are consistent with the hypothesis that during cerebral ischemia, the BBB Na-K-Cl cotransporter is stimulated to mediate transendothelial uptake of Na into the brain and that increased cotransporter activity also contributes to gradual swelling of the cells.