Carsten M E, Miller J D
J Biol Chem. 1977 Mar 10;252(5):1576-81.
A microsomal fraction resembling striated muscle sarcoplasmic reticulum was isolated from uterine smooth muscle. ATP induces calcium accumulation in this fraction. Increased temperature enhances calcium accumulation and calcium-activated ATPase. In the absence of ATP, approximately 35% of the intrinsic calcium exchanges with the 45Ca in the incubation medium. In the presence of ATP, exchange of intrinsic calcium with 45Ca increases by an amount which equals the ATP-dependent calcium binding. In preparations partially preloaded with calcium, a steady state of bound calcium is reached when the ATP is exhausted. Calcium is released under these conditions by prostaglandins E2 and F2alpha, but not by PGF1beta. The antibiotic ionophores X537A and A23187, as well as oxytocin, also release calcium previously accumulated under ATP stimulation. None of these agents, with the exception of oxytocin, release intrinsic calcium. Thus, the effect of prostaglandins resembles that of the ionophores, suggesting an ionophoretic action of these prostaglandins. The release of calcium conforms with the in vivo smooth muscle contracting action of these agents.
从子宫平滑肌中分离出一种类似于横纹肌肌浆网的微粒体部分。ATP可诱导该部分积累钙。温度升高会增强钙的积累和钙激活的ATP酶。在没有ATP的情况下，约35%的内源性钙与孵育介质中的45Ca进行交换。在有ATP的情况下，内源性钙与45Ca的交换量增加，增加的量等于ATP依赖性钙结合量。在部分预先加载钙的制剂中，当ATP耗尽时达到钙结合的稳态。在这些条件下，前列腺素E2和F2α可释放钙，但PGF1β不能。抗生素离子载体X537A和A23187以及催产素也可释放先前在ATP刺激下积累的钙。除催产素外，这些物质均不释放内源性钙。因此，前列腺素的作用类似于离子载体，提示这些前列腺素有离子载体样作用。钙的释放与这些物质在体内的平滑肌收缩作用相符。
