Collins P L, Zink E, Moore R M, Roberts J M, Maguire M E, Moore J J
Department of Obstetrics and Gynecology, University of California, San Francisco.
Am J Obstet Gynecol. 1993 Jan;168(1 Pt 1):143-51. doi: 10.1016/s0002-9378(12)90904-7.
Human amnion is important in the initiation of labor. Ritodrine, when administered as a tocolytic, is found unchanged in amniotic fluid. We characterized effects of ritodrine binding to beta-adrenergic receptors in amnion and amniocytes.
Iodine 125-iodopindolol, beta-adrenergic receptor agonists, and beta-adrenergic receptor antagonists were used to describe binding characteristics. Experiments were designed with and without isoproterenol and ritodrine to study intracellular cyclic adenosine 3'5'-monophosphate and prostaglandin E2 release.
Scatchard analysis revealed a single class of saturable binding sites, with maximum binding capacity of 70.0 +/- 17.2 fmol/mg protein (n = 12) and with high-affinity dissociation constant of 458.9 +/- 72.1 pmol/L. Agonists and antagonists competed for the 125I-iodopindolol binding site consistent with a beta 2-adrenergic receptor. Hill coefficients were 0.6 to 0.8 for agonist competition and 1.0 for antagonist competition and ritodrine. Stimulation with isoproterenol resulted in dose-dependent increases in cyclic adenosine 3'5'-monophosphate and prostaglandin E2. Ritodrine failed to stimulate cyclic adenosine 3'5'-monophosphate and inhibited isoproterenol-stimulated cyclic adenosine 3'5'-monophosphate and prostaglandin E2 production.
In human amnion binding of ritodrine to beta 2-adrenergic receptors and lack of ritodrine-mediated postreceptor effects are characteristic of a beta 2-adrenergic antagonist.
人羊膜在分娩发动中起重要作用。利托君作为宫缩抑制剂使用时，在羊水中未发生变化。我们对利托君与羊膜和羊膜细胞中β - 肾上腺素能受体结合的效应进行了表征。
使用碘125 - 碘吲哚洛尔、β - 肾上腺素能受体激动剂和β - 肾上腺素能受体拮抗剂来描述结合特性。设计了有无异丙肾上腺素和利托君的实验，以研究细胞内环磷酸腺苷3',5'-单磷酸和前列腺素E2的释放。
Scatchard分析显示存在一类单一的可饱和结合位点，最大结合容量为70.0±17.2 fmol/mg蛋白质（n = 12），高亲和力解离常数为458.9±72.1 pmol/L。激动剂和拮抗剂竞争125I - 碘吲哚洛尔结合位点，这与β2 - 肾上腺素能受体一致。激动剂竞争的希尔系数为0.6至0.8，拮抗剂竞争和利托君的希尔系数为1.0。异丙肾上腺素刺激导致环磷酸腺苷3',5'-单磷酸和前列腺素E2呈剂量依赖性增加。利托君未能刺激环磷酸腺苷3',5'-单磷酸，并抑制异丙肾上腺素刺激的环磷酸腺苷3',5'-单磷酸和前列腺素E2的产生。
在人羊膜中，利托君与β2 - 肾上腺素能受体的结合以及利托君介导的受体后效应的缺乏是β2 - 肾上腺素能拮抗剂的特征。
