Activation of gastro-intestinal smooth muscle induced by the calcium ionophore A23187

Abstract

Summary Tension development was recorded in isolated smooth muscle preparations from the guineapig, namely circular strips from the fundus and antrum region of the stomach, and taenia coli. The calcium ionophore A23187 (2·10⁻⁶–2·10⁻⁵ mol/l) induced maximum activity in fundus and taenia coli, and in antrum an activity slightly smaller than that obtained with acetylcholine (ACh) (5·10⁻⁶ mol/l). The ionophore-induced activity could be suppressed by so-called calcium antagonists: D600 (3·10⁻⁶ mol/l) suppressed the ionophore-induced activity of taenia coli completely; phasic and tonic components in the stomach preparations were selectively suppressed by D600 and sodium nitroprusside (10⁻⁶ mol/l), respectively.