Acetylcholine and ATP hyperpolarize endothelium via activation of different types of Ca(2+)-activated K+ channels.

Experiments on rat thoracic aorta showed that ATP and acetylcholine hyperpolarize endothelial cell via selective activation of low (SK) and intermediate (IR) conductance Ca(2+)-activated K(+)channels, respectively. It was hypothesized that ATP- and acetylcholine-activated Ca(2+)-signals are spatially separated and generated in plasma membrane regions with predominant localization of SK- and IR-channels, respectively.