Yeagley C, Caritis S N, Ruzycky A L
Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, PA, USA.
Am J Obstet Gynecol. 1996 May;174(5):1637-42. doi: 10.1016/s0002-9378(96)70621-x.
This study tested the hypothesis that gestational age and agonist concentration are important determinants of beta-adrenergic-dependent myometrial contraction inhibition.
In vitro concentration-response curves for ritodrine and terbutaline were generated with myometrial strips collected from 21-day-pregnant rats. The in vitro efficacy of ritodrine (0.1 mumol/L) was evaluated in tissue from 15-, 18-, and 21-day animals. Contractile responses were analyzed by computer and normalized to a control potassium response.
The degree of the inhibitory effects of both drugs was concentration dependent over the range of 0.01 to 10 mumol/L. The duration of contraction inhibition progressively decreased from 15 to 21 days of pregnancy.
The degree of tachyphylaxis with beta-agonists is dependent on and increases with the gestational age of the target tissue. beta-Agonist type was not an important determinant of the duration of inhibitory response. We speculate that the effect of gestational age on tachyphylaxis may be related to increased myometrial expression of inactivating beta-adrenergic receptor kinases.
本研究检验了以下假设，即胎龄和激动剂浓度是β-肾上腺素能依赖性子宫肌层收缩抑制的重要决定因素。
用从妊娠21天的大鼠收集的子宫肌条生成利托君和特布他林的体外浓度-反应曲线。在来自妊娠15天、18天和21天动物的组织中评估利托君（0.1μmol/L）的体外效力。通过计算机分析收缩反应，并将其标准化为对照钾反应。
在0.01至10μmol/L的范围内，两种药物的抑制作用程度均呈浓度依赖性。收缩抑制的持续时间从妊娠15天到21天逐渐缩短。
β-激动剂快速减敏的程度取决于靶组织的胎龄，并随胎龄增加。β-激动剂类型不是抑制反应持续时间的重要决定因素。我们推测胎龄对快速减敏的影响可能与子宫肌层中失活的β-肾上腺素能受体激酶表达增加有关。
