Simultaneous Measurement of [Ca2+]i and Membrane Potential under Mechanical or Biochemical Stimulation

In human umbilical endothelial cells (HUVEC), mechanical stress is known to induce transients of [Ca²⁺]_i that lead to the regulation of vascular functions in vivo. The transmembraneous influx of Ca²⁺ is thought to be mediated by voltage-dependent ion channels or stretch-activated ion channels. In order to elucidate the correlation of [Ca²⁺]_i and membrane potential under mechanical stress, the influences of mechanical or biochemical stimulation on endothelial cells stained with both fura-2 and DiBAC₄(3) were studied in vitro, by constructing an imaging system that could capture four kinds of fluorescence images simultaneously at real-time. In the application of thrombin, [Ca²⁺]_i transients were accompanied with preceding depolarization, while mechanical stress that were loaded on a single cell with a micropipette did not evoke dramatic changes of membrane potential. These results indicate that the signaling pathway initiated by mechanical stress could be independent of electrochemical activation, and different from that by biochemical stimulation in HUVEC.