Ion channels in capillary endothelium.

Vascular beds are anatomically and functionally compartmentalized into arteries, capillaries, and veins. The bulk of the vasculature consists of the dense, anastomosing capillary network, composed of capillary endothelial cells (cECs) that are intimately associated with the parenchyma. Despite their abundance, the ion channel expression and function and Ca²⁺ signaling behaviors of capillaries have only recently begun to be explored in detail. Here, we discuss the established and emerging roles of ion channels and Ca²⁺ signaling in cECs. By mining a publicly available RNA-seq dataset, we outline the wide variety of ion channel genes that are expressed in these cells, which potentially imbue capillaries with a broad range of sensing and signal transduction capabilities. We also underscore subtle but critical differences between cEC and arteriolar EC ion channel expression that likely underlie key functional differences in ECs at these different levels of the vascular tree. We focus our discussion on the cerebral vasculature, but the findings and principles being elucidated in this area likely generalize to other vascular beds.