PROPAGATION OF CALCIUM WAVES BETWEEN COLONIC SMOOTH-MUSCLE CELLS IN CULTURE

Intercellular propagation of a diffusible substance through direct cyt oplasmic communication between multiple cells could represent an impor tant mechanism for mutual multiple cell signaling between cells in a t issue. The current study was aimed at characterizing the mechanism(s) underlying the intercellular propagation of calcium concentration ([Ca 2+](i)) transients between colonic smooth muscle cells. Changes in [Ca 2+](i) in smooth muscle cells from the rabbit distal colon in primary cultures were monitored using videomicroscopy with the fluorescent dye Fura-2. Myocytes responded to light mechanical deformation of the pla sma membrane with a localized increase in [Ca2+](i) which spread in a wave-like fashion through up to 5 adjacent cells, with little change i n wave amplitude. Dye coupling between cells was demonstrated by Lucif er Yellow, and intercellular wave propagation was abolished by octanol , suggesting propagation of Ca2+ waves via gap junctions. Wave propaga tion was not dependent on extracellular [Ca2+], suggesting regenerativ e release of Ca2+ from intracellular stores. Propagation of Ca2+ waves through silent cells suggested a diffusible messenger other than Ca2. Wave propagation and kinetics were unaffected by ryanodine (50 mu M) or caffeine (10 mM), but abolished by depletion of thapsigargin-sensi tive Ca2+ stores and by the phospholipase C inhibitor U-73122 (10 mu M ), implicating inositol 1,4,5-trisphosphate (Ins(1,4,5)P-3,) sensitive stores as the major Ca2+ source for propagated Ca2+ transients. These results indicate that, in a connected complex of colonic smooth muscl e cells in culture, multiple cells can monitor the mechanical status o f a single cell through diffusion of Ins(1,4,5)P-3, Ca2+, or another i ntercellular messenger.