Caritis S N, Chiao J P, Kridgen P
Department of Obstetrics and Gynecology, University of Pittsburgh School of Medicine, Magee-Womens Hospital, PA 15213.
Am J Obstet Gynecol. 1991 Apr;164(4):1005-11; discussion 1011-2. doi: 10.1016/0002-9378(91)90574-b.
In this study we compare the uterine contractility and beta-adrenergic receptor effects of identical doses of ritodrine administered intermittently or continuously for 24 hours in pregnant sheep. Ritodrine was administered intravenously to five animals as a pulse, 16 micrograms/kg every 1.5 hours, whereas five other animals received ritodrine as a continuous infusion of 0.18 microgram/kg/min. Ritodrine plasma concentrations at steady state were comparable in both groups and averaged 18 ng/ml. Animals receiving ritodrine pulses demonstrated no alteration of myometrial beta-adrenergic receptors or adenylyl cyclase activity, and ritodrine inhibited oxytocin-induced contractility comparably at 4 and 24 hours. Animals receiving ritodrine continuously had a significant decrease in myometrial beta-adrenergic receptors and adenylyl cyclase activity, yet ritodrine inhibition of oxytocin-induced uterine contractility was sustained for 24 hours. Oxytocin receptors were not affected by ritodrine administration and were similar in both groups. At the dose studied, oxytocin-induced contractions are comparably inhibited by ritodrine for 24 hours whether the drug is given continuously or in a pulsatile fashion.
在本研究中，我们比较了相同剂量的利托君在怀孕绵羊中持续24小时间歇性或连续性给药时的子宫收缩力及β-肾上腺素能受体效应。对5只动物静脉注射利托君脉冲剂量，每1.5小时16微克/千克，而另外5只动物接受利托君以0.18微克/千克/分钟的速度持续输注。两组利托君稳态血浆浓度相当，平均为18纳克/毫升。接受利托君脉冲给药的动物子宫肌层β-肾上腺素能受体或腺苷酸环化酶活性未发生改变，且利托君在4小时和24小时时对催产素诱导的收缩具有相当的抑制作用。持续接受利托君的动物子宫肌层β-肾上腺素能受体和腺苷酸环化酶活性显著降低，但利托君对催产素诱导的子宫收缩的抑制作用持续24小时。催产素受体不受利托君给药的影响，两组相似。在所研究的剂量下，无论利托君是持续给药还是脉冲给药，其对催产素诱导的收缩的抑制作用持续24小时。
