Thulesius O, Lunell N O, Ibrahim M, Moberger B, Angilivilayil C
Department of Pharmacology-Toxicology, Faculty of Medicine, Kuwait University.
Acta Obstet Gynecol Scand. 1987;66(3):237-40. doi: 10.3109/00016348709020754.
Because of results in animal experiments which demonstrated a partial beta 2-adrenoceptor activity of labetalol on rat uterine smooth muscle the present study was conducted in human preparations. The following results were obtained: 1. Rhythmic uterine contractions with a defined steady-state amplitude and frequency were elicited spontaneously and after methylergometrine. 2. Labetalol reduced amplitude of contractions dose-dependently after 3 h of incubation. Frequency was unaffected. 3. The tocolytic effect of labetalol is apparent only at high concentrations, above those used in the treatment of hypertension. 4. Neither beta 2-specific adrenoceptor blockade with ICI 118,551 nor alpha-blockade with phentolamine changed amplitude of contraction, either alone or in combination with labetalol. 5. Labetalol has little tocolytic effect on human myometrium in vitro. This effect is unrelated to alpha- or beta-antagonism, but seems to depend on a direct smooth muscle depressant effect. In conclusion, from the present in vitro experiments using human myometrial preparations, it seems unlikely that labetalol would interfere with the normal process of labor when used for the treatment of pregnancy hypertension.
由于动物实验结果表明拉贝洛尔对大鼠子宫平滑肌具有部分β2肾上腺素能受体活性，因此本研究在人体标本上进行。获得了以下结果：1. 自发以及在甲基麦角新碱作用后可诱发具有明确稳态幅度和频率的节律性子宫收缩。2. 孵育3小时后，拉贝洛尔剂量依赖性地降低收缩幅度。频率未受影响。3. 拉贝洛尔的宫缩抑制作用仅在高于治疗高血压所用浓度的高浓度时才明显。4. 单独使用ICI 118,551进行β2特异性肾上腺素能受体阻滞或使用酚妥拉明进行α阻滞，无论单独使用还是与拉贝洛尔联合使用，均未改变收缩幅度。5. 拉贝洛尔在体外对人子宫肌层几乎没有宫缩抑制作用。这种作用与α或β拮抗作用无关，但似乎取决于直接的平滑肌抑制作用。总之，从目前使用人子宫肌层标本的体外实验来看，拉贝洛尔用于治疗妊娠高血压时似乎不太可能干扰正常分娩过程。
