title: Interaction of acetylcholine and cholecystokinin with dispersed smooth muscle cells.
abstract: Isolated gastric smooth muscle cells were prepared from the stomach of Bufo marinus by successive incubation in collagenase without added trypsin. Contraction was determined by image-splitting micrometry and expressed as the mean percentage decrease in cell length from control. Peak contractile response was attained within 30 s. Dose-response curves constructed from peak responses showed that the maximal responses to CCK-OP (37.2 +/- 3.8%), acetylcholine (35.3 +/- 2.5%), and Ca2+ (42.3 +/- 0.9%) were similar. The D50s for octapeptide of cholecystokinin (CCK-OP) and acetylcholine were around 10(-12) M and 10(-11) M, respectively. The response to a combination of submaximal concentrations of acetylcholine and CCK-OP exceeded the individual responses but did not exceed the maximal response to either agent alone. A low concentration of atropine (5 X 10(-10) M) inhibited specifically the maximal response to acetylcholine. A high concentration of atropine (5 X 10(-8) M) inhibited partially the maximal response to CCK-OP but had no effect on the maximal response to Ca2+. It was concluded that 1) dispersed gastric smooth muscle cells are highly sensitive to stimulation; 2) CCK-OP has a direct (myogenic) contractile effect on gastric smooth muscle; and 3) the effect of CCK-OP and acetylcholine are mediated by separate receptors.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002024:Bufo marinus; D002118:Calcium / Q000494:pharmacology; D002766:Cholecystokinin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000166:cytology* / Q000187:drug effects; D013270:Stomach
chemical_list: D001285:Atropine; D002766:Cholecystokinin; D000109:Acetylcholine; D002118:Calcium