在兔肠系膜动脉中，A23187增加储存部位的钙通透性比增加表面膜的钙通透性更多。
A23187 increases calcium permeability of store sites more than of surface membranes in the rabbit mesenteric artery.
作者信息
Itoh T, Kanmura Y, Kuriyama H
出版信息
J Physiol. 1985 Feb;359:467-84. doi: 10.1113/jphysiol.1985.sp015597.
The effects of a Ca ionophore, A23187, were investigated on intact and skinned smooth muscle tissues of the rabbit mesenteric artery. A23187 (over 10(-9) M) inhibited, dose dependently, contractions induced by 10(-5) M-noradrenaline (NA) or 10 mM-caffeine in Ca2+-free solution containing 2 mM-EGTA. Procaine (3 mM) led to cessation of the caffeine- or NA-induced contractions in the presence or absence of Ca2+. When A23187 (10(-7) M) was applied, the contractions in the presence of procaine were to some extent restored in Krebs solution. A23187 at a concentration of 10(-7) M did not modify the resting muscle tone, but this concentration did increase the amplitude of the contraction evoked by 20.2 or 128 mM-K+ and markedly inhibited the 10(-7) M-NA or 10 mM-caffeine-induced contraction in Krebs solution. A23187 (10(-7) M) delayed the onset and rising phase of the 10(-5) M-NA-induced contraction with inhibition of the oscillatory contractions. High concentrations of A23187 (over 10(-6) M) produced a large contraction in the presence and a small contraction in the absence of 2.6 mM-Ca2+. These A23187-induced contractions were not inhibited by 10(-7) M-nisoldipine, a Ca2+ antagonist. A23187 (over 10(-6) M) applied for a long period functionally skinned the muscle tissues. However, the Ca2+ sensitivity of the A23187-treated skinned muscles was lower than that of saponin-treated muscles. In saponin-treated skinned muscles, A23187 (below 10(-6) M) had no effect on the pCa-tension relation. After filling the store, A23187 (over 10(-7) M) generated a larger contraction than did caffeine in Ca2+-free solution, in the presence or absence of 5 mM-NaN3. When 10(-7) M-A23187 was applied once for 5 min, subsequently applied caffeine (20 mM), following application of Ca2+, no longer produced contraction of skinned muscle tissues. The present results indicate that low concentrations of A23187 show a selective Ca2+-releasing action on Ca2+ store sites in muscle cells and that high concentrations increase the Ca2+ leakage (influx) and the cell membrane is skinned.
研究了钙离子载体A23187对兔肠系膜动脉完整和平滑肌组织条的作用。在含2 mM乙二胺四乙酸（EGTA）的无钙溶液中，A23187（浓度超过10⁻⁹ M）能剂量依赖性地抑制由10⁻⁵ M去甲肾上腺素（NA）或10 mM咖啡因诱导的收缩。在有或无Ca²⁺存在的情况下，3 mM普鲁卡因可使咖啡因或NA诱导的收缩停止。当应用A23187（10⁻⁷ M）时，在Krebs溶液中，普鲁卡因存在时的收缩在一定程度上得以恢复。浓度为10⁻⁷ M的A23187不会改变静息肌张力，但该浓度确实增加了由20.2或128 mM K⁺诱发的收缩幅度，并显著抑制了Krebs溶液中10⁻⁷ M NA或10 mM咖啡因诱导的收缩。A23187（10⁻⁷ M）延迟了10⁻⁵ M NA诱导收缩的起始和上升阶段，并抑制了振荡性收缩。高浓度的A23187（超过10⁻⁶ M）在有2.6 mM Ca²⁺存在时产生大的收缩，在无Ca²⁺时产生小的收缩。这些A23187诱导的收缩不受10⁻⁷ M尼索地平（一种Ca²⁺拮抗剂）的抑制。长时间应用超过10⁻⁶ M的A23187会使肌肉组织在功能上发生去膜。然而，经A23187处理的去膜肌肉的Ca²⁺敏感性低于经皂角苷处理的肌肉。在经皂角苷处理的去膜肌肉中，低于10⁻⁶ M的A23187对pCa-张力关系无影响。在储存库充盈后，在有或无5 mM叠氮化钠的情况下，在无钙溶液中，超过10⁻⁷ M的A23187比咖啡因产生更大的收缩。当一次性应用10⁻⁷ M A23187 5分钟后，随后应用咖啡因（20 mM），再加入Ca²⁺时，去膜肌肉组织不再产生收缩。目前的结果表明，低浓度的A23187对肌肉细胞中的Ca²⁺储存位点具有选择性的Ca²⁺释放作用，而高浓度则增加Ca²⁺泄漏（内流）并使细胞膜去膜。
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