Calcium waves in colonic myocytes produced by mechanical and receptor-mediated stimulation.
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.
D000818:Animals; D001696:Biomechanical Phenomena; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D003106:Colon / Q000378:metabolism*; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D010812:Physical Stimulation; D011817:Rabbits; D012433:Ryanodine / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology