Aims: Endothelin-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 Ca(2+) in smooth muscle cells (SMC) of renal resistance arteries.
Main methods: In in vitro studies of primary SMC, which were isolated from rat renal microvessels, the levels of intracellular Ca(2+) 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 Ca(2+) indicator Fluo-4 AM.
Key findings: The two-photon imaging demonstrates that treatment of isolated rat renal resistance arteries with ET-1 causes a rapid increase of intracellular Ca(2+) 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 Ca(2+) in cultured SMC to 510±83nM.
Significance: ET-1-mediated elevation of intracellular Ca(2+) is strongly linked to renal microvascular contraction and is crucial for ET-1-induced contraction of SMC. The two-photon imaging of intracellular Ca(2+) in intact SMC of rat renal resistance arteries is a powerful technique which allows the detailed ex vivo analysis of intracellular Ca(2+) handling by ET-1, an important player in hypertension-related kidney diseases.
Keywords: Contraction; Fluo-4 AM; Microvasculature; Renal resistance arteries.
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