Application of real-time confocal microscopy to intracellular calcium ion dynamics in rat arterioles

. The regulation of cytosolic Ca 2+ homeostasis is essential for cells, including vascular smooth muscle cells. Arterial tone, which underlies the maintenance of peripheral resistance in the circulation, is a major contributor to the control of blood pressure. Confocal microscopy was employed to study the alteration in intracellular calcium ion concentration ([Ca 2+ ] i ) in arterioles (external diameters <100 µm) with respect to selected modifying reagents. 5-Hydroxytryptamine (1 µM), ATP (10 µM), and endothelin 1–3 (5 nM) elicited an increase in [Ca 2+ ] i in most arteriole smooth muscle cells. The [Ca 2+ ] i increase sometimes propagated in an intercellular manner. When noradrenaline (10 µM) was used as a stimulant, [Ca 2+ ] i increase was observed only in a portion of the smooth muscle cells. It was also noted that the reaction of these cells with respect to ATP is different between testis and brain arterioles; the [Ca 2+ ] i increase in testicular arterioles is dependent on Ca 2+ influx from extracellular space, whereas in cerebral arterioles it plays a role in both the influx of extracellular Ca 2+ and the release of Ca 2+ from intracellular stores (i.e., sarco/endoplasmic reticulum). These results indicate that arterioles in different tissues may differ greatly in their responses. Real-time confocal microscopy was found to be a useful tool for investigating the structural and functional changes in living tissues.