Murray J J, Reed P W, Fay F S
Proc Natl Acad Sci U S A. 1975 Nov;72(11):4459-63. doi: 10.1073/pnas.72.11.4459.
Ionophore A23187 causes contraction of smooth muscle cells isolated from the stomach muscularis of Bufo marinus. The peak response is reached within 10 sec of inophore addition and then decays to a lesser, sustained contraction. The initial phase of contraction is maximal at A23187 concentrations greater than 5 X 10(-6) M and half maximal at 5 X 10(-7) M. Chelation of extracellular calcium by ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) does not affect the initial contraction produced by A23187, whereas it inhibits completely the sustained, secondary phase. Addition of calcium in excess of EGTA restores this phase rapidly and fully to control levels of contraction. A23187 produces a maximal, rapid contraction of muscle cells previously depolarized by incubation in high potassium medium. The ionophore also contracts isolated strips of stomach smooth muscle. A23187 appears to produce contraction of the isolated smooth muscle cells by transmembrane transport of calcium into the cytoplasm from both intracellular and extracellular sources.
离子载体A23187可使从海蟾蜍胃肌层分离出的平滑肌细胞发生收缩。在加入离子载体后的10秒内达到最大反应，随后衰减为较小的持续性收缩。收缩的初始阶段在A23187浓度大于5×10⁻⁶ M时最大，在5×10⁻⁷ M时为最大反应的一半。用乙二醇双（β-氨基乙基醚）-N,N'-四乙酸（EGTA）螯合细胞外钙并不影响A23187产生的初始收缩，而它完全抑制了持续性的第二阶段收缩。加入过量于EGTA的钙可迅速且完全地将此阶段恢复到对照收缩水平。A23187可使先前在高钾培养基中孵育而发生去极化的肌肉细胞产生最大程度的快速收缩。该离子载体还可使分离的胃平滑肌条收缩。A23187似乎通过将钙从细胞内和细胞外来源跨膜转运到细胞质中，从而使分离的平滑肌细胞发生收缩。
