Ward S M, Caritis S N, Chiao J P, Moore J J
Department of Obstetrics and Gynecology, University of Pittsburgh School of Medicine, Magee-Womens Hospital, PA 15213.
Am J Obstet Gynecol. 1988 Dec;159(6):1461-6. doi: 10.1016/0002-9378(88)90575-3.
We have previously demonstrated in pregnant sheep that ritodrine infusion for 24 hours reduces myometrial beta-adrenergic receptor density and isoproterenol-stimulated adenylate cyclase activity. These receptor-associated changes were accompanied by an increasing inability of ritodrine to inhibit uterine contractility induced by a bolus of oxytocin. In the present study, we evaluated whether these ritodrine-induced effects could be altered by dexamethasone. Ten pregnant sheep at gestational ages of 92 to 130 days received ritodrine 2 micrograms/kg/min for 24 hours. Five animals also received dexamethasone 10 mg intravascularly twice during the ritodrine infusion. Before and at 4 and 24 hours of ritodrine infusion, the animals were given an identical dose of oxytocin as a bolus, and the area under the uterine pressure-time curve was quantified. Myometrial biopsy specimens were obtained before and after ritodrine infusion. Dexamethasone treatment prevented ritodrine-induced reductions in beta-adrenergic receptor density and isoproterenol-stimulated adenylate cyclase activity. Despite these receptor-associated effects, dexamethasone did not prevent the loss of tocolytic efficacy associated with prolonged ritodrine infusion.
我们之前在妊娠绵羊中证实，输注利托君24小时可降低子宫肌层β - 肾上腺素能受体密度以及异丙肾上腺素刺激的腺苷酸环化酶活性。这些与受体相关的变化伴随着利托君抑制大剂量催产素诱导的子宫收缩能力的逐渐下降。在本研究中，我们评估了地塞米松是否能改变这些利托君诱导的效应。10只妊娠92至130天的绵羊接受2微克/千克/分钟的利托君输注24小时。5只动物在输注利托君期间还两次静脉注射10毫克地塞米松。在输注利托君前以及输注4小时和24小时时，给动物静脉注射相同剂量的催产素作为一次大剂量给药，并对子宫压力 - 时间曲线下面积进行量化。在输注利托君前后获取子宫肌层活检标本。地塞米松治疗可防止利托君诱导的β - 肾上腺素能受体密度降低以及异丙肾上腺素刺激的腺苷酸环化酶活性降低。尽管有这些与受体相关的效应，但地塞米松并不能防止因长时间输注利托君而导致的宫缩抑制疗效丧失。
