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      Calcium-Release-Activated Calcium Influx in Endothelium

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          Signaling pathways activated by the tachykinin substance P (SP) were investigated in pig coronary artery endothelial cells (PCAECs). Single cells were obtained after enzymatic digestion of coronary arteries. Intracellular Ca<sup>2+</sup> ([Ca<sup>2+</sup>]i) was measured from fura-2 fluorescence while membrane potential or ionic current was measured using patch-clamp techniques. In physiological saline solution, SP induced hyperpolarizations or outward currents which coincided with biphasic [Ca<sup>2+</sup>]i increases representing store release of Ca<sup>2+</sup> and Ca<sup>2+</sup> influx. Single channel recording protocols showed that both sources of Ca<sup>2+</sup> activated a small conductance K<sup>+</sup> channel, resulting in cell hyperpolarization. When outward currents were blocked by d-tubocurare, Cs<sup>+</sup>, or BAP-TA, an inward current was unmasked. Ion substitution protocols showed that the SP-induced inward current was (1) carried by a mixture of Ca<sup>2+</sup> and Na<sup>+</sup>, (2) blocked by La<sup>3+</sup>, and (3) inactivated by high extracellular [Ca<sup>2+</sup>]. Tyrosine kinase inhibitors also blocked the inward current. The same current was activated by bath application of BHQ, an inhibitor of the endoplasmic reticulum Ca<sup>2+</sup> ATPase, or by cell dialysis with IP3. These results suggest that the plateau phase of the agonist-activated [Ca<sup>2+</sup>]i increase in PCAECs reflects Ca<sup>2+</sup> entry through a depletion-activated Ca<sup>2+</sup> channel. The characteristics of this channel are compared to those of Ca<sup>2+</sup> channels found in other nonexcitable cells.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          24 September 2008
          : 34
          : 3
          : 186-195
          Department of Medical Physiology, Texas A&M University Health Science Center, College Station, Tex., USA
          159222 J Vasc Res 1997;34:186–195
          © 1997 S. Karger AG, Basel

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          Pages: 10


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