Nasu Y
Nihon Heikatsukin Gakkai Zasshi. 1982 May;18(2):75-82.
The relaxing effect of isoprenaline on [Na+]o-free induced contracture of the guinea-pig taenia coli was investigated in presence of phentolamine (10(-5)M), an alphareceptor blocking agent. This action of isoprenaline showed dose-dependency (ED 50: 10(-5)M) and was abolished completely by beta-receptor blocking agent (propranolol, 10(-5)M). The effect of isoprenaline (10(-5)M) disappeared gradually during long exposure to [Na+]o-free solution and when short application of sodium ions to the perfusing solution, the effect of isoprenaline was restored. Pretreatment of [K+]o-free solution or ouabain (10(-5)M) enhanced the effect of isoprenaline. The effect of isoprenaline is inhibited by ouabain (10(-5)M) by about 50%. These observations strongly suggest that the inhibitory effect of isoprenaline may be mainly mediated through activation of Na-pump. However, direct activation of the drug on Na+-Ca2+ exchange, Ca-pump, or Ca-uptake into cellular Ca store sites can not be ruled out.
在存在α受体阻断剂酚妥拉明（10⁻⁵M）的情况下，研究了异丙肾上腺素对无钠诱导的豚鼠结肠带挛缩的舒张作用。异丙肾上腺素的这一作用呈剂量依赖性（半数有效剂量：10⁻⁵M），并被β受体阻断剂（普萘洛尔，10⁻⁵M）完全消除。在长时间暴露于无钠溶液期间，异丙肾上腺素（10⁻⁵M）的作用逐渐消失，而当向灌注溶液中短暂加入钠离子时，异丙肾上腺素的作用得以恢复。用无钾溶液或哇巴因（10⁻⁵M）预处理可增强异丙肾上腺素的作用。哇巴因（10⁻⁵M）可使异丙肾上腺素的作用抑制约50%。这些观察结果强烈表明，异丙肾上腺素的抑制作用可能主要通过激活钠泵介导。然而，不能排除该药物对钠钙交换、钙泵或钙摄入细胞钙储存位点的直接激活作用。
