Mechanism of intracellular Ca2+-wave propagation elicited by mechanical stimulation in cultured endothelial CPAE cells

Intra- and intercellular Ca2+-signaling during mechanical stimulation in calf pulmonary artery endothelial cells (CPAE) was investigated with digital fluorescence microscopy. Mechanical stimulation of a CPAE cell in a Ca2+-containing solution revealed a rise of the free intracellular Ca2+-concentration ([Ca2+]i) in the mechanically stimulated cell (MS) proceeding to the neighboring (NB) cells as an intercellular Ca2+-wave. Experiments in Ca2+-free solution, containing 2mM EGTA, demonstrated that a detectable [Ca2+]i-transient in the MS cell is not always a requisite for intercellular communication (IC). The Ca2+-wave propagation was not affected by changes in membrane potential and was not mediated by voltage-dependent Ca2+-channels. Ca2+-influx through the Ni2+-sensitive Ca2+-pathway occurred in the MS as could be assessed by Mn2+-quenching experiments. The intra- and intercellular Ca2+-wave was triggered by the release of thapsigargin-sensitive intracellular Ca2+-stores. Phospholipase C (PLC) inhibition by U73122 reduced the Ca2+-amplitude of the MS cell and almost completely inhibited the IC, indicating that the Ca2+-release in the MS and NB cells is PLC/inositol 1,4,5-trisphosphate (IP3) mediated.