Study on the Inhibitory Effects of Progesterone on Myometrial Contractions

Abstract

1) Progesterone showed the early effect that myometrial contractions were temporarily promoted by progesterone in vitro. The effect is very interesting, because progesterone accelerated the binding of ACh with depot protein and receptor.
Progesterone in vitro had no effects in the early stage on oxytocic actions of accelerating myometrial contractions and the binding of ACh with depot protein and receptor.
2) As the time elapsed progesterone continuously accelerated the binding of ACh with depot protein; however it disturbed ACh on its binding with receptor. These results may relate to the inhibited myometrial contractions which followed the early accelerated contractions under the influence of progesterone in vitro.
Progesterone weakened oxytocic actions on myometrial contractions and the binding of ACh with tissue protein, as the late effects.
3) The labor provoking mechanism was explained from the standpoint of myometrial ACh.