Kawarabayashi T, Tsukamoto T, Hamasaki Y, Kaneko Y, Ikeda M, Sugimori H
Department of Obstetrics and Gynecology, Saga Medical School, Japan.
Gynecol Obstet Invest. 1991;31(3):130-5. doi: 10.1159/000293119.
The relationship between contraction changes and cAMP production under long-term application of ritodrine was investigated using longitudinal muscle strips of pregnant (Day 21) rat uterus. Cellular cAMP gradually increased up to 20 min, then decreased to the control level and fluctuated after 90 min in the presence of 1.5 x 10(-7) M ritodrine. When the dose was raised to 3.1 x 10(-4) M, cAMP contents markedly increased. However, it then decreased after 30 min and reached the control level after 180 min. To clarify the actual relationship between the changes in spontaneous contraction and cAMP contents of the same muscle strips, the strips were obtained during control contraction, suppression by 1.5 x 10(-7) M ritodrine and reactivation after suppression in the presence of the drug. Consequently, the cAMP content of reactivated muscle was significantly lower than that of suppressed muscle (p less than 0.01), however it was still higher than the control (p less than 0.05). It is speculated that the reactivation of spontaneous contractions might not depend solely on the cellular cAMP level, and that another activating mechanism, such as changes in ion permeability, might be involved in this type of desensitization phenomenon.
使用妊娠（第21天）大鼠子宫的纵行肌条研究了长期应用利托君时收缩变化与环磷酸腺苷（cAMP）产生之间的关系。在存在1.5×10⁻⁷ M利托君的情况下，细胞内cAMP在20分钟内逐渐增加，然后降至对照水平，并在90分钟后波动。当剂量提高到3.1×10⁻⁴ M时，cAMP含量显著增加。然而，30分钟后它又下降，180分钟后达到对照水平。为了阐明同一肌条的自发收缩变化与cAMP含量之间的实际关系，在对照收缩期间、1.5×10⁻⁷ M利托君抑制期间以及抑制后在药物存在下重新激活期间获取肌条。结果，重新激活的肌肉的cAMP含量显著低于抑制的肌肉（p＜0.01），然而它仍高于对照（p＜0.05）。推测自发收缩的重新激活可能不仅仅取决于细胞内cAMP水平，并且这种脱敏现象可能涉及另一种激活机制，例如离子通透性的变化。
