A new technique for simultaneous and in situ measurements of Ca2+ signals in arteriolar smooth muscle and endothelial cells

We report here the first local and global Ca2+ measurements made from in situ terminal arterioles. The advantages of the method are that there is minimal disturbance to the vessels, which retain their relationship to the tissue they are supplying (rat ureter) and the small size of vessel that can be studied. Good loading with the Ca2+ indicator, Fluo-4 was obtained, and confocal sectioning through the tissue enabled vascular smooth muscle and endothelial cells to be clearly seen, along with red blood cells, nerve endings and the ureteric smooth muscle cells. We find the terminal arterioles to be extremely active, both spontaneously and in response to nor-adrenaline stimulation, with Ca2+ sparks occurring in the vascular myocytes and Ca2+ puffs in the endothelial cells. Even under resting conditions, endothelial cells produced oscillations and waves, which could pass from cell to cell, whereas the vascular myocytes only produced waves in response to agonist stimulation, and with no increase in the frequency of Ca2+ sparks, and no spread from cell to cell. We compare our data to those obtained in dissected intact vessels and single cells. We conclude that this approach is a convenient and useful method for studying inter- and intracellular Ca2+ signalling events and communication between cell types, particularly in very small vessels. © 2003 Elsevier Science Ltd. All rights reserved.