Endocardial TRPC-6 Channels Act as Atrial Mechanosensors and Load-Dependent Modulators of Endocardial/Myocardial Cross-Talk
Vesna Nikolova-Krstevski, Soeren Wagner, Ze Yan Yu, Charles D. Cox, Jasmina Cvetkovska, Adam P. Hill, Inken G. Huttner, Victoria Benson, Andreas A. Werdich, Calum MacRae, Michael P. Feneley, Oliver Friedrich, Boris Martinac and Diane Fatkin
Ca2+ Measurements in AE Cells Exposed to Acute Unidirectional Cyclic Stretch
(A) Increases in intracellular calcium levels ([Ca2+]i) due to external Ca2+ entry were demonstrated by augmentation of Fluo-4 signals in stretched AE cells (right panels) but not in control cells (left panels). Fluorescence recordings were initiated after acute cyclic stretch holding at maximum distension while confocal imaging. (B) Quantitative time curves of Ca2+ entry into AE cells in control cells (n = 37), and in cells stretched at 5% (n = 58) and 10% (n = 72) intensity. Bar graph shows mean increase in [Ca2+]i at different stretch intensities. (C) Representative time curves of Ca2+ entry after 10% stretch in control (n = 45) and stretched AE cells pre-treated with inhibitors of mechanosensitive (GsMTx-4; n = 55), store-operated (2-aminoethoxydiphenyl borate [2-APB]; n = 60) and voltage-gated (nifedipine; n = 55) Ca2+ channels. Bar graphs for mean data are shown. (D) Addition of TRPC-6-specific pore-blocking (TRPC-6 Ab) attenuated Ca2+ influx in 10% stretched cells (control: n = 40; 10% stretch: n = 36; 10% stretch + TRPC-6 Ab: n = 38). For (B to D), internal stores were pre-emptied with thapsigargin to rule out contributions from internal endoplasmic reticulum Ca2+ release to F/F0. Data are shown as mean ± SEM. *p < 0.001 versus control cells; ❖p < 0.001 versus 10% stretch. See Supplemental Video 1. Abbreviations as in Figures 1 and 2.