CSN3 and Hyperkalemia: Although these are not direct evidence of the inhibitory effect of hyperkalemia on endothelial KCa channel activity, given that KCa activation requires [Ca2+]i rise and membrane depolarization in endothelial cells decreases the driving force for Ca2+ entry, suppression of KCa activity therefore may be expected when vascular endothelium is exposed to hyperkalemic cardioplegia/organ preservation solutions.