Recruitment of Smooth Muscle Cells and Intercellular Calcium Waves during Arterial Vasomotion

Abstract

AbstractVasomotion is a natural property of small arteries and arterioles. Vasomotion consists in cyclic diameter variations, which are induced by synchronous contractions of the smooth muscle cells (SMCs) present in the arterial wall. These contractions have been shown to be due to an increase in the SMCs cytosolic calcium concentration. The present study was performed on rat mesenteric arterial strips. The first part investigated the response of SMCs under different concentrations of phenylephrine (PE), a vasoconstrictor, with an emphasis on the synchronization of SMCs in endothelium denuded strips. We observed that the recruitment of the SMCs increased with the PE concentration and vasomotion appeared only when a sufficient number of SMCs were recruited and synchronized.Intercellular calcium oscillations propagating along the strips have been observed during vasomotion. In the second part of this study, we were able to measure the speed of the intercellular calcium waves, which was about 100 μm/s. Using a software developed in our laboratory, we managed to track the contraction of the arterial strip and to measure the velocity of the contraction wave which was, as expected, of the same order as the calcium wave velocity. Experiments where the endothelium was still present were also performed and the velocity of contraction was calculated. We also obtained a speed of approximately 100 μm/s. The fact that the contraction waves speed stayed unchanged between strips with or without endothelium showed that the endothelium was not the pathway for the signal leading to intercellular calcium propagations during vasomotion.KeywordsSmooth Muscle CellCalcium WaveTracking SoftwareIntact EndotheliumContraction WaveThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.