Mostwin J L
J Urol. 1985 May;133(5):900-5. doi: 10.1016/s0022-5347(17)49277-9.
Study of the in vitro behavior of strips of guinea pig bladder and taenia coli demonstrated that: Both bladder and taenia temporarily retain their ability to contract in Ca-free solutions, but the magnitude of this response decays with time. Carbachol is capable of producing contraction in Ca-free solution for a longer period of time than K depolarisation. Once lost, the ability of carbachol (but not K) to contract the tissues in Ca-free solution can be temporarily restored by a brief application of high Ca. The size of the carbachol contraction in Ca-free solution is reduced in Na-free solution, suggesting that membrane-bound Ca may not play a major role in this response. In depolarised bladder exposed to nifedipine 2 X 10(-7) M, carbachol can only elicit 1 large contraction, suggesting depletion of an intracellular source. It is concluded that whereas the response of the bladder to depolarisation depends primarily on extracellular Ca, the response to carbachol may also involve release of stored Ca and that the bladder, like other smooth muscles, appears to contain agonist-releasable intracellular Ca stores.
膀胱和结肠带在无钙溶液中都能暂时保持收缩能力，但这种反应的幅度会随时间衰减。与钾去极化相比，卡巴胆碱在无钙溶液中产生收缩的时间更长。一旦丧失，通过短暂应用高钙可暂时恢复卡巴胆碱（而非钾）在无钙溶液中使组织收缩的能力。在无钠溶液中，无钙溶液中卡巴胆碱收缩的幅度减小，这表明膜结合钙可能在这种反应中不起主要作用。在暴露于2×10⁻⁷M硝苯地平的去极化膀胱中，卡巴胆碱只能引发1次大的收缩，提示细胞内钙源耗尽。结论是，虽然膀胱对去极化的反应主要取决于细胞外钙，但对卡巴胆碱的反应可能还涉及储存钙的释放，并且膀胱与其他平滑肌一样，似乎含有可被激动剂释放的细胞内钙储存。
