AimsEndothelin-1 (ET-1) is a potent vasoconstrictor which regulates the physiology of cardiorenal system. The aim of this study was to evaluate ET-1-mediated elevation of intracellular Ca2+ in smooth muscle cells (SMC) of renal resistance arteries. Main methodsIn in vitro studies of primary SMC, which were isolated from rat renal microvessels, the levels of intracellular Ca2+ were calculated from the ratio of emissions at 340 and 380nm after loading cells with Fura 2-AM dye. In ex vivo studies we used two-photon imaging of renal resistance arteries excised from rat kidneys and loaded with fluorescent Ca2+ indicator Fluo-4 AM. Key findingsThe two-photon imaging demonstrates that treatment of isolated rat renal resistance arteries with ET-1 causes a rapid increase of intracellular Ca2+ concentration in smooth muscle vasculature of these vessels. These ex vivo observations are in accordance with in vitro findings indicating that ET-1 mediates activation of TRPC channels and increases the level of intracellular Ca2+ in cultured SMC to 510±83nM. SignificanceET-1-mediated elevation of intracellular Ca2+ is strongly linked to renal microvascular contraction and is crucial for ET-1-induced contraction of SMC. The two-photon imaging of intracellular Ca2+ in intact SMC of rat renal resistance arteries is a powerful technique which allows the detailed ex vivo analysis of intracellular Ca2+ handling by ET-1, an important player in hypertension-related kidney diseases.