Ca²⁺-Images of Smooth Muscle Cells and Endothelial Cells in One Confocal Plane in Femoral Artery Segments of the Rat

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Simultaneous recording of Ca²⁺-images in one confocal plane from vascular smooth muscle cells (SMCs) and endothelial cells (ECs) of an intact rat femoral artery segment was performed using indo-1 and a confocal microscope. During application of 10 μM acetylcholine (ACh), elevation and oscillation of intracellular Ca²⁺ concentration ([Ca²⁺]_i) were observed in ECs but not in SMCs. Sequential conduction of Ca²⁺ oscillation from an EC to the neighboring ECs in one longitudinal direction was often observed in the presence of ACh. On the other hand, the activation of voltage-dependent Ca²⁺ channels by external 30 mM K⁺ resulted in the elevation of [Ca²⁺]_i only in SMCs. When 10 μM ACh was added in the presence of 30 mM K⁺, it was observed in one confocal plane that [Ca²⁺]_i in ECs and SMCs was almost simultaneously increased and decreased, respectively. The simultaneous recording method in this intact preparation will provide a line of valuable information about the interactions between SMCs and ECs, based on spatio-temporal analyses of absolute values of [Ca²⁺]_i in individual cells.