Simultaneous arterial calcium dynamics and diameter measurements: application to myoendothelial communication

The goal of the present study was to analyze the intercellular calcium comm unication between smooth muscle cells (SMCs) and endothelial cells (ECs) by simultaneously monitoring artery diameter and intracellular calcium concen tration in a rat mesenteric arterial segment in vitro under physiological p ressure (50 mmHg) and flow (50 mul/min) in a specially developed system. In tracellular calcium was expressed as the fura 2 ratio. The diameter was mea sured using a digital image acquisition system. Stimulation of SMCs with th e alpha (1)-agonist phenylephrine (PE) caused not only an increase in the f ree intracellular calcium concentration of the SMCs as expected but also in the ECs, suggesting a calcium flux from the SMCs to the ECs. The gap junct ion uncoupler palmitoleic acid greatly reduced this increase in calcium in the ECs on stimulation of the SMCs with PE. This indicates that the signali ng pathway passes through the gap junctions. Similarly, although vasomotion originates in the SMCs, calcium oscillates in both SMCs and ECs during vas omotion, suggesting again a calcium flux from the SMCs to the ECs.