Calcium waves in colonic myocytes produced by mechanical and receptor-mediated stimulation
Young, S.H.; Ennes, H.S.; McRoberts, J.A.; Chaban, V.V.; Dea, S.K.; Mayer, E.A.
American Journal of Physiology 276(5): G1204-G1212
1999
ISSN/ISBN: 0002-9513 PMID: 10330011 Document Number: 508272
The mechanisms underlying intracellular Ca2+ waves induced by either mechanical or receptor-mediated stimulation of myocytes isolated from the longitudinal muscle layer of the rabbit distal colon were compared using fura 2 and fluorescence videomicroscopy. Light focal mechanical deformation of the plasma membrane or focal application of substance P resulted in localized intracellular Ca2+ concentration ([Ca2+]i) transients that propagated throughout the cell. In both cases, the Ca2+ response consisted of a transient peak response followed by a delayed-phase response. Substance P-mediated [Ca2+]i responses involved generation of inositol 1,4,5-trisphosphate and release of Ca2+ from thapsigargin-sensitive stores, whereas mechanically induced responses were partially (29%) dependent on La3+-sensitive influx of extracellular Ca2+ and partially on release of intracellular Ca2+ from thapsigargin-insensitive stores gated by ryanodine receptors. The delayed-phase response in both cases was dependent on extracellular Ca2+. However, although the response to substance P was sensitive to La3+, that after mechanical stimulation was not. In the later case, the underlying mechanism may involve capacitative Ca2+ entry channels that are activated after mechanical stimulation but not by substance P. Reprinted by permission of the publisher.