Casper R F, Lye S J
Am J Obstet Gynecol. 1986 Feb;154(2):301-5. doi: 10.1016/0002-9378(86)90660-5.
Infusion of the long-acting beta-adrenergic agonist ritodrine (3 micrograms/kg/min) caused by rapid inhibition of uterine activity in the ovariectomized, nonpregnant sheep. This inhibition could only be maintained for 6.4 +/- 0.8 hours, with high-frequency activity returning by 11.4 +/- 2.6 hours despite continuous infusion of ritodrine. Intermittent administration of ritodrine did not prolong uterine relaxation, probably as a consequence of its long half-life. Continuous infusion of the short-acting beta-agonist isoproterenol (0.16 micrograms/kg/min) initially inhibited uterine contractions but high-frequency activity returned by 50 minutes. In contrast, intermittent infusion of isoproterenol (30 minutes on and 30 minutes off) significantly inhibited the frequency of contractions during each of the infusion periods for the duration of the study (13 hours). Our data demonstrate that either continuous administration of beta-agonists or intermittent administration of the long-acting beta-agonist ritodrine resulted in myometrial desensitization in the sheep. In contrast, intermittent administration of the short-acting beta-adrenergic agonist isoproterenol prevented the onset of myometrial desensitization.
给去卵巢的未孕绵羊输注长效β-肾上腺素能激动剂利托君（3微克/千克/分钟）可迅速抑制子宫活动。这种抑制作用只能维持6.4±0.8小时，尽管持续输注利托君，但高频活动在11.4±2.6小时时又恢复了。间歇性给予利托君并不能延长子宫松弛时间，这可能是由于其半衰期长所致。持续输注短效β-激动剂异丙肾上腺素（0.16微克/千克/分钟）最初可抑制子宫收缩，但50分钟后高频活动又恢复了。相比之下，间歇性输注异丙肾上腺素（输注30分钟，停30分钟）在研究持续时间（13小时）内的每个输注期均显著抑制了收缩频率。我们的数据表明，持续给予β-激动剂或间歇性给予长效β-激动剂利托君都会导致绵羊子宫肌层脱敏。相比之下，间歇性给予短效β-肾上腺素能激动剂异丙肾上腺素可防止子宫肌层脱敏的发生。
