Relaxin action on myometrial contractility

作为补助金第一年（平成2）期间的初步实验，分别从妊娠（17-22天）大鼠的子宫中分离纵向和环形肌条，并进行绝育和雌激素致敏（雌二醇17 β注射后1-3天）。将肌条暴露于36 ℃的人工盐水介质（Krebs组合物）中，并检查机械、电活动以及响应于猪松弛素的环AMP含量的变化。松弛素（50- 150 mU）对妊娠第17天的猪子宫平滑肌收缩抑制几乎无效。松弛素对环肌的收缩有轻微的抑制作用，而在外部镁离子的存在下，环肌的收缩抑制作用增强。这一观察结果与松弛素受体在环肌层占主导地位的发现一致，在妊娠第17天达到峰值（Mercado-Simmen 1980，1982）。在雌激素致敏大鼠的纵肌和环肌中，松弛素即使在缺乏外部镁的情况下也能有效地引起收缩抑制。因此，在第二年（平成3年），实验集中在上述标本上，同时，对胶原酶处理的妊娠大鼠子宫肌层单个分离细胞的电测量进行了挑战。仅从由5-6个细胞组成的批次记录平台电位。接口附件和膜片钳版本55（Compac）由补助金购买，用于此目的。

As pilot experiments during the first year of grant-in-aid (Heisei 2), the longitudinal and circular muscle strips were separately isolated from uteri of pregnant (17-22 day), and spayed and estrogen-primed (1-3 days after estradiol 17beta injection) rats. The muscle strips were exposed to artificial saline media (Krebs composition) at 36 ﾟC, and mechanical, electrical activities, and changes in cyclic AMP content in response to porcine relaxin were examined. Porcine relaxin was provided from NIH, USA.Relaxin (50-150mU) was nearly ineffective in causing contractile depression in the longitudifnal muscle taken from uteri on 17 pregnant day. The contraction of the circular muscle was slightly depressed by relaxin, and the contractile depression was potentiated in the presence of external Mg ions. This observation is compatible with the finding that relaxin receptor dominates the circular muscle layer and it attains its peak on 17 pregnant day (Mercado-Simmen 1980, 1982).In both the longitudinal and circular muscles of estrogen-primed rats, relaxin was very effective in causing a contractile depression even in the absense of external Mg. Therefore, in the following year (Heisei 3), experiments were focussed on the above specimen.At the same time, the electrical measurements on single isolated cell of pregnant rat myometrium by collagenase treatment were challenged. The plateau potential was recorded only from a batch consisted of 5-6 cells. The interface attachment and patch clamp version 55 (Compac) purchased by the grant-in-aid, was used for this purpose.