EXPERIMENTAL STUDIES ON THE RELATIONSHIP BETWEEN MYOMETRIAL PROGESTERONE AND UTERINE CONTRACTION

The relation between myometrial progesterone and uterine contrac tion was investigated determining the content of progesterone in myometrium of the rat at the time of gestation and labor using the thin layer chromato graphy and the gas liquid chromatography. With the progress of gestation the myometrial progesterone increased in quantity, but decreased rapidly with the onset of labor. Castration, hypophysectomy or adrenalectomy during gestation more or less lowered the myometrial content of progesterone. The one side (horn) of a pregnant uterus in labor contained less progesterone than the other side (horn), which was not yet in labor. The injection of progesterone elevates its level in myometrium, while estrogen or oxytocin has no influence on the content of progesterone in myometrium. Out of the results stated above, it is assumed that the myometrial progesterone has some intimate relationships with actomyosin ATPase activity of the myometrium, which is inhibited in pregnancy and accelerated with the onset of labor.