Coordinated calcium signaling within isolated microvascular endothelial cell tubes

Endothelial cell (EC) Ca +2 signaling is integral to regulating smooth muscle cell (SMC) relaxation. Because SMC activity can influence Ca +2 signaling in ECs, our goal was to investigate Ca +2 signaling in native microvascular ECs in the absence of SMCs. Mouse abdominal muscle feed arteries were dissected and SMCs were dissociated to yield intact endothelial cell tubes (~70 μm wide, ~1 mm long). After loading with Fluo‐4, tubes (n=6) were superfused (2.5 ml/min, ~24 °C) and imaged (120 frames/s) using spinning disc confocal microscopy. Within the field of view (~35 ECs), Ca +2 signaling was minimal at rest. Brief (0.1 mM, 2 s) or sustained (1 μM) ACh superfusion initially increased Ca +2 in all ECs followed by secondary Ca +2 oscillations. Frame‐by‐frame analyses of latencies for Ca +2 elevations between ECs were evaluated as an index of coordinated activity. During the initial response to ACh, latencies for Ca +2 elevations were similar between ECs (200–400 ms; p>0.05). In contrast, during secondary oscillations, latencies for Ca +2 elevations between adjacent ECs were less (p<0.01) than between nonadjacent ECs for either brief (500 ± 60 vs. 1620 ± 140 ms) or sustained (430 ± 30 vs. 1140 ± 230 ms) ACh exposure. These observations within intact microvascular endothelial cell tubes indicate coordinated Ca +2 signaling between neighboring cells. (NIH R37‐ HL041026 , R01‐ HL086483 , F32‐ HL097463 , T32‐ AR048523 )