Blood–Brain Barrier KCa3.1 Channels Evidence for a Role in Brain Na Uptake and Edema in Ischemic Stroke

Background and Purpose—KCa3.1, a calcium-activated potassium channel, regulates ion and fluid secretion in the lung and gastrointestinal tract. It is also expressed on vascular endothelium where it participates in blood pressure regulation. However, the expression and physiological role of KCa3.1 in blood–brain barrier (BBB) endothelium has not been investigated. BBB endothelial cells transport Na+ and Cl− from the blood into the brain transcellularly through the co-operation of multiple cotransporters, exchangers, pumps, and channels. In the early stages of cerebral ischemia, when the BBB is intact, edema formation occurs by processes involving increased BBB transcellular Na+ transport. This study evaluated whether KCa3.1 is expressed on and participates in BBB ion transport. Methods—The expression of KCa3.1 on cultured cerebral microvascular endothelial cells, isolated microvessels, and brain sections was evaluated by Western blot and immunohistochemistry. Activity of KCa3.1 on cerebral microvascular en...