Vasomotion in human arteries and their regulations based on ion channel regulations: 10 years study

Vasomotion is the oscillation of vascular tone which gives rise to flow motion of blood into an organ. As is well known, spontaneous contractile organs such as heart, GI, and genitourinary tract produce rhythmic contraction. It imposes or removes pressure on their vessels alternatively for exchange of many substances. It was first described over 150 years ago, however the physiological mechanism and pathophysiological implications are not well understood. This study aimed to elucidate underlying mechanisms and physiological function of vasomotion in human arteries. Conventional contractile force measurement, immunohistochemistry, and Western blot analysis were employed to study human left gastric artery (HLGA) and uterine arteries (HUA). RESULTS: Circular muscle of HLGA and/or HUA produced sustained tonic contraction by high K⁺ (50 mM) which was blocked by 2 µM nifedipine. Stepwise stretch and high K⁺ produced nerve-independent spontaneous contraction (vasomotion) (around 45% of tested tissues). Vasomotion was also produced by application of BayK 8644, 5-HT, prostagrandins, oxytocin. It was blocked by nifedipine (2 µM) and blockers of intracellular Ca²⁺ stores. Inhibitors of Ca²⁺ -activated Cl^- channels (DIDS and/or niflumic acid) and ATP-sensitive K⁺ (K_ATP ) channels inhibited vasomotion reversibly. Metabolic inhibition by sodium cyanide (NaCN) and several neuropeptides also regulated vasomotion in K_ATP channel-sensitive and -insensitive manner. Finally, we identified TMEM16A Ca²⁺ -activated Cl^- channels and subunits of K_ATP channels (Kir 6.1/6.2 and sulfonylurea receptor 2B [SUR2B]), and c-Kit positivity by Western blot analysis. We conclude that vasomotion is sensitive to TMEM16A Ca²⁺ -activated Cl^- channels and metabolic changes in human gastric and uterine arteries. Vasomotion might play an important role in the regulation of microcirculation dynamics even in pacemaker-related autonomic contractile organs in humans.