Electrical coupling between endothelial cells and smooth muscle cells in hamster feed arteries - Role in vasomotor control

Endothelial cells (ECs) govern smooth muscle cell (SMC) tone via the release of paracrine factors (eg, NO and metabolites of arachidonic acid). We tested the hypothesis that ECs can promote SMC relaxation or contraction via direct electrical coupling. Vessels (resting diameter, 57+/-3 mu m; length, 4 mm) were isolated, cannulated, and pressurized (75 mm Hg; 37 degrees C). Two microelectrodes were used to simultaneously impale 2 cells (ECs or SMCs) in the vessel wall separated by 500 mu m. Impalements of one EC and one SMC (n = 26) displayed equivalent membrane potentials at rest, during spontaneous oscillations, and during hyperpolarization and vasodilation to acetylcholine, Injection of -0.8 nA into an EC caused hyperpolarization (approximate to 55 mV) and relaxation of SMCs (dilation, approximate to 5 mu m) along the vessel segment. In a reciprocal manner, +0.8 nA caused depolarization (approximate to 2 mV) of SMCs with constriction (approximate to 2 mu m). Current injection into SMCs while recording from ECs produced similar results. We conclude that ECs and SMCs are electrically coupled to each other in these vessels, such that electrical signals conducted along the endothelium can be directly transmitted to the surrounding smooth muscle to evoke vasomotor responses.