Ca2+ signaling in injured in situ endothelium of rat aorta

The inner watt of excised rat aorta was scraped by a microelectrode and Ca2+ signals were investigated by fluorescence microscopy in endothetial cells (ECs) directly coupled with injured cells. The injury caused an immediate increase in the intracellular Ca2+ concentration ([Ca2+](i)), followed by a long-lasting decay phase due to Ca2+ influx from extracellular space. The immediate response was mainly due to activation of purinergic receptors, as shown by the effect of P-2X and P-2Y receptors agonists and antagonists, such as suramin, alpha,beta-MeATP, MRS-2179 and 2-MeSAMP. Inhibition of store-operated Ca2+ influx did not affect either the peak response or the decay phase. Furthermore, the latter was: (i) insensitive to phospholipase C inhibition, (ii) sensitive to the gap junction blockers, palmitoleic acid, heptanol, octanol and oleamide, and (iii) sensitive to La3+ and Ni2+, but not to Gd3+. Finally, ethidium bromide or Lucifer Yellow did not enter ECs facing the scraped area. These results suggest that endothelium scraping: (i) causes a short-tasting stimulation of healthy ECs by extracellular nucleotides released from damaged cells and (ii) uncouples the hemichannels of the ECs facing the injury site; these hemichannels do not fully close and allow a long-lasting Ca2+ entry. (C) 2007 Elsevier Ltd. All rights reserved.