title: Calcium pools mobilized during excitation-contraction coupling in flounder intestinal smooth muscle.
abstract: The effects of Ca2+ free solutions (0 mM Ca2+/5mM EGTA) and low Ca2+ media (no added Ca2+) on the 100 mM K+ and 10(-5) M ACh contractions of the flounder intestine were examined. Ca2+-free solutions abolished the K+-contractions and reduced the normal ACh response to a smaller transient event. Low Ca2+ media blocked the prolonged tonic phase of the K+-contractions more readily than the initial phasic component. It was concluded that both ACh and K+ stimulate Ca2+ entry into the cell and that the phasic component of the K+-contraction relies on a more tightly bound extracellular Ca2+-fraction than that utilized during the tonic phase. ACh can also mobilize an intracellular Ca2+-store. Ultrastructural studies suggested that this ACh-releasable intracellular Ca2+-store may reside on the inner surface of the plasma membrane or within the peripheral S.R.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D005399:Fishes; D007422:Intestines; D007473:Ion Channels; D008854:Microscopy, Electron; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D011189:Potassium Chloride / Q000494:pharmacology; D012508:Sarcolemma / Q000648:ultrastructure; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure
chemical_list: D007473:Ion Channels; D004533:Egtazic Acid; D011189:Potassium Chloride; D000109:Acetylcholine; D002118:Calcium