Propagation of fast and slow intercellular Ca 2+ waves in primary cultured arterial smooth muscle cells

Abstract

Smooth muscle contraction is regulated by changes in cytosolic Ca 2+ concentration ([Ca 2+] i ). In response to stimulation, Ca 2+ increase in a single cell can propagate to neighbouring cells through gap junctions, as intercellular Ca 2+ waves. To investigate the mechanisms underlying Ca 2+ wave propagation between smooth muscle cells, we used primary cultured rat mesenteric smooth muscle cells (pSMCs). Cells were aligned with the microcontact printing technique and a single pSMC was locally stimulated by mechanical stimulation or by microejection of KCl. Mechanical stimulation evoked two distinct Ca 2+ waves: (1) a fast wave (2 mm/s) that propagated to all neighbouring cells, and (2) a slow wave (20 μm/s) that was spatially limited in propagation. KCl induced only fast Ca 2+ waves of the same velocity as the mechanically induced fast waves. Inhibition of gap junctions, voltage-operated calcium channels, inositol 1,4,5-trisphosphate (IP 3) and ryanodine receptors, shows that the fast wave was due to gap junction mediated membrane depolarization and subsequent Ca 2+ influx through voltage-operated Ca 2+ channels, whereas, the slow wave was due to Ca 2+ release primarily through IP 3 receptors. Altogether, these results indicate that temporally and spatially distinct mechanisms allow intercellular communication between SMCs. In intact arteries this may allow fine tuning of vessel tone.