Connexins in the vasculature

Vascular function requires the highly coordinated behavior of individual cells. The modulation of vascular resistance and blood flow required to match oxygen delivery to a wide dynamic range of tissue needs can be achieved only by coordinated diameter changes over large distances along the vessel. This is accomplished by longitudinal long-distance communication through the vessel wall by gap junctions. The vascular endothelial cells are structurally suited for this task and are coupled extraordinarily well to form a functional unit within the vessel wall. Cx40 is the most abundant connexin in the vascular endothelium. Its loss results in functional deficits, such as hypertension and a lack of coordination of vascular responses. Gap junctions also couple the vascular smooth muscle cells. These intercellular junctions are formed by Cx43, though evidence of Cx45 expression has been provided recently. In addition, gap junctions interconnect endothelial and smooth muscle cells heterocellularly to create short-distance transverse pathways. This theoretically allows reciprocal direct communication pathways between the cells of these two vascular compartments and could potentially provide for the function of the elusive endothelium-derived hyperpolarizing factor.