Noguera M A, Calatayud S, D'Ocon M P
Departamento de Farmacología, Facultad de Farmacia, Universidad de Valencia, Burjassot, Spain.
Naunyn Schmiedebergs Arch Pharmacol. 1993 Nov;348(5):472-7. doi: 10.1007/BF00173205.
In isolated rat aortic strips noradrenaline induces a biphasic contractile response in Ca-free medium, associated with two different intracellular calcium pools, one of which is common to caffeine. We analyzed the mechanisms involved in the depletion and repletion of both intracellular Ca pools sensitive to noradrenaline in different experimental procedures in presence of prazosin, phentolamine and yohimbine. At 37 degrees C the alpha-adrenergic blocking agents inhibited contractile responses to noradrenaline in Ca-free medium, with prazosin being highly selective. alpha 2-adrenoceptors probably do not participate in the release of Ca from internal stores, as no contractile response was observed after addition of clonidine in Ca-free medium. This indicates that noradrenaline-induced Ca-release from internal stores is mainly due to activation of alpha 1-adrenoceptors. At 25 degrees C, these compounds failed to inhibit caffeine-induced contraction in Ca-free medium, but abolished the release of Ca from an intracellular store only sensitive to noradrenaline. This effect is attributable to a blockade of alpha 1-adrenoceptors and/or inhibition of receptor-mediated signal transduction.
在分离的大鼠主动脉条中，去甲肾上腺素在无钙培养基中诱导双相收缩反应，这与两种不同的细胞内钙库有关，其中一个钙库对咖啡因也有反应。我们在存在哌唑嗪、酚妥拉明和育亨宾的不同实验程序中，分析了对去甲肾上腺素敏感的两种细胞内钙库的耗竭和补充所涉及的机制。在37℃时，α-肾上腺素能阻断剂抑制无钙培养基中对去甲肾上腺素的收缩反应，哌唑嗪具有高度选择性。α2-肾上腺素能受体可能不参与从内部储存库释放钙，因为在无钙培养基中加入可乐定后未观察到收缩反应。这表明去甲肾上腺素诱导的从内部储存库释放钙主要是由于α1-肾上腺素能受体的激活。在25℃时，这些化合物未能抑制无钙培养基中咖啡因诱导的收缩，但消除了仅对去甲肾上腺素敏感的细胞内储存库释放钙的现象。这种效应归因于α1-肾上腺素能受体的阻断和/或受体介导的信号转导的抑制。
