Distinct potentials in the myoendothelial junction

Abstract

Myoendothelial junctions (MEJ) bridge the smooth muscle cells (SMCs) and endothelial cells (ECs) in small arteries. In most vessels they project from the EC through the internal elastic lamina and into the SMC, where gap junctions connect the MEJ with the SMC. MEJs are characterised by a long thin neck and on top a “head”, which can be coupled to SMCs with gap junctions. We have used a spatiotemporal model to simulate electrical coupling between the two cell types. The model shows that the MEJ could be electrically isolated from both the EC and the SMC due to the long thin neck and that there could be levels of cations and anions in the MEJ that are different from the EC and SMC bulk levels. Local Ca2+ domains in the MEJ can activate an outward K+ current in the MEJ and we found that activation of less than 10–20 K+ channels (e.g. IK channels) is sufficient to create an electrical potential of 1–5 mV between the SMC and MEJ. This suggests that the MEJ should be considered as a unique structure with properties distinct from those of the smooth muscle cells or of the endothelial cells proper. Supported by The Danish Council for Independent Research ‐ Medical Sciences.