Ca2+-images of smooth muscle cells and endothelial cells in one confocal plane in femoral artery segments of the rat

Simultaneous recording of Ca2+-images in one confocal plane from vascular s mooth muscle cells (SMCs) and endothelial cells (ECs) of an intact rat femo ral artery segment was performed using indo-1 and a confocal microscope. Du ring application of 10 muM acetylcholine (ACh), elevation and oscillation o f intracellular Ca2+ concentration ([Ca2+](i)) were observed in ECs but not in SMCs. Sequential conduction of Ca2+ oscillation from an EC to the neigh boring ECs in one longitudinal direction was often observed in the presence of ACh. On the other hand, the activation of voltage-dependent Ca2+ channe ls by external 30 mM K+ resulted in the elevation of [Ca2+](i) only in SMCs . When 10 muM 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 simultaneousl y increased and decreased, respectively. The simultaneous recording method in this intact preparation will provide a line of valuable information abou t the interactions between SMCs and ECs, based on spatio-temporal analyses of absolute values of [Ca2+](i) in individual cells.