Differential regulation of intracellular Ca2+ signalling induced by high K+ and endothelin-1 in single smooth muscle cells of intact canine basilar artery: Detection by means of confocal laser microscopy

Changes in intracellular calcium concentration ([Ca2+](i)) in smooth muscle cells play the key role in regulation of vascular smooth muscle tone and p athogenesis of cerebral vasospasm. In this study, we adopted the confocal l aser microscopy to detect the fluorescence signals arising from the individ ual smooth muscle cells of canine basilar artery. Ring preparations were ma de, loaded with fluo-3 and changes in fluorescence induced by high K+ and e ndothelin-l (ET-1) were measured by confocal laser microscopy. In some unst imulated smooth muscle cells Ca2+ waves arising from discrete region of the cell propagated to the whole cell with a velocity of similar to 10 mu m/s. High K+ (80 mmol/L) induced a rapid rise in [Ca2+](i), the peak level bein g consistently reached approximately 10 s after stimulation. In contrast, t he time to peak level of [Ca2+](i) induced by ET-1 (0.3 mu mol/L) varied wi dely between 13 and 26 s among individual cells, an indication that the ext ent of nonuniform coordination of increases in [ca(2+)](i) in individual ce lls may be partly responsible for the different time courses of tension dev elopment of vascular smooth muscle in response to the vasoactive stimulants . The increase in [Ca2+](i) induced by ET-1 was transient but a pronounced and sustained contraction developed further in response to ET-1. Thus ET-1 has a biological property as a potential candidate to elicit cerebral vasos pasm. Confocal laser microscopy could be a useful tool to measure the chang es in [Ca2+](i) in individual smooth muscle cells of cerebral artery.