Endogenous Acetylcholine Detected by Changes in [Ca 2+ ] i Within Isolated Endothelial Cell Tubes

Abstract

Stimulation of muscarinic acetylcholine (ACh) receptors expressed on the surface of endothelial cells (ECs) provides a powerful vasodilator response. However, these cells are not directly innervated, so it is unknown where endogenous ACh originates to activate the receptors. There is a considerable body of evidence to suggest that ACh can originate from non-neuronal sources, so we investigated the possibility that blood cells may provide or stimulate the production of ACh. To assess the potential source of ACh, we freshly prepared EC tubes from isolated rat mesenteric arteries and measured [Ca2+]i changes reported with Oregon Green® 488 BAPTA-1. To characterize this newly developed model, exogenous ACh was added and reproducibly stimulated asynchronous Ca2+ waves that propagated through the cytoplasm in >95% of ECs. Application of rat whole blood to the EC tubes initiated a transient but robust increase in the frequency of EC Ca2+ events (from 1.27 ± 0.19 basally to 5.18 ± 0.37 events.min-1) and the numbe...