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+)) in arterioles (external diameters <100 microm) with respect to selected modifying reagents. 5-Hydroxytryptamine (1 microM), ATP (10 microM), and endothelin 1-3 (5 nM) elicited an increase in Ca(2+) in most arteriole smooth muscle cells. The Ca(2+) increase sometimes propagated in an intercellular manner. When noradrenaline (10 microM) was used as a stimulant, Ca(2+) 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+) 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.