Calixto J B
Gen Pharmacol. 1987;18(3):237-43. doi: 10.1016/0306-3623(87)90005-x.
The sustained contractions induced by K+, acetylcholine (ACh) and oxytocin (Ot) were inhibited in a concentration-dependent fashion by diphenylhydantoin (DPH) and nifedipine (NIF) in the following order of sensitivity: K+ greater than ACh greater than Ot. Previous incubation of DPH and NIF produced a non-competitive antagonism towards ACh and Ot-induced contractions. Increasing of calcium (Ca2+) concentration (0.2-1.5 mM) completely reverse the inhibitory effect of DPH and NIF, suggesting a competitive type of antagonism, between Ca2+ and DPH. A clear difference between DPH and NIF actions was observed when the K+-depolarizing solution was used. In this condition, DPH caused a parallel and concentration-related rightward displacement of the dose-response curves of Ca2+ (pA2 = 4.91 +/- 0.1), while NIF produced a rightward displacement allied to a significant reduction of the Ca2+ maximal response. DPH, but not NIF, produced a concentration-dependent relaxation in sustained contraction induced by Ca2+ (1 mM) in depolarized tissue.
苯妥英（DPH）和硝苯地平（NIF）以浓度依赖的方式抑制由钾离子（K⁺）、乙酰胆碱（ACh）和催产素（Ot）诱导的持续收缩，其敏感性顺序如下：K⁺＞ACh＞Ot。预先孵育DPH和NIF会对ACh和Ot诱导的收缩产生非竞争性拮抗作用。增加钙（Ca²⁺）浓度（0.2 - 1.5 mM）可完全逆转DPH和NIF的抑制作用，表明Ca²⁺与DPH之间存在竞争性拮抗作用。当使用K⁺去极化溶液时，观察到DPH和NIF作用之间存在明显差异。在这种情况下，DPH导致Ca²⁺剂量 - 反应曲线平行且与浓度相关的右移（pA2 = 4.91 ± 0.1），而NIF产生右移并伴有Ca²⁺最大反应的显著降低。在去极化组织中，DPH而非NIF在由Ca²⁺（1 mM）诱导的持续收缩中产生浓度依赖性舒张。
