Karaki H, Kubota H, Urakawa N
Eur J Pharmacol. 1979 Jun 15;56(3):237-45. doi: 10.1016/0014-2999(79)90176-6.
In Ca-free solution norepinephrine (NE) produced only a phasic contraction in the media-intima layer of rabbit aorta. The second application of NE was almost ineffective. Incubation of the muscle with Ca for a short period (Ca loading) restored the ability to produce a phasic contraction in Ca-free solution. Various ions and compounds were applied to the muscle prior to the Ca loading or prior to NE application and it was found that these treatments variously affected the NE-induced phasic contraction. The data suggest that the NE-induced phasic contraction in Ca-free solution results from Ca release from cellular sites and that a hyperbolic relationship exists between the amount of Ca at these sites and the magnitude of the contraction. These sites take up extracellular Ca by a process sensitive to La3+ but not to D600; the Ca influx stimulated by high K solution, which is sensitive to D600 and also contributes to refilling of these sites; NE releases this stored Ca by a process sensitive to procaine, caffeine and theophylline and, in this manner, elicits a phasic contraction.
在无钙溶液中，去甲肾上腺素（NE）仅在兔主动脉中膜 - 内膜层引起一个单相收缩。再次应用NE几乎无效。将肌肉短期用钙孵育（钙负荷）可恢复在无钙溶液中产生单相收缩的能力。在钙负荷之前或NE应用之前，将各种离子和化合物应用于肌肉，发现这些处理对NE诱导的单相收缩有不同影响。数据表明，无钙溶液中NE诱导的单相收缩是由细胞部位释放钙引起的，并且这些部位的钙量与收缩幅度之间存在双曲线关系。这些部位通过对La3 +敏感但对D600不敏感的过程摄取细胞外钙；高钾溶液刺激的钙内流对D600敏感，也有助于这些部位的再填充；NE通过对普鲁卡因、咖啡因和茶碱敏感的过程释放这种储存的钙，并以这种方式引发单相收缩。
