Cholinesterase activity in the myometrium, placenta and serum of the rats

Abstract

It is a well known fact that Cholinesterase (ChE) is important in acetylcholine cycle. Moreover, it has been assumed that uterine contraction might be related to ChE activity in myometrium. ChE activities of rat myometrium were observed in sexual cycle, various stages of pregnancy and puerperium by Hesterin-Miyazaki method. The effects of castration, administration of sexual hormones and contraction induced by various substances were investigated on ChE activities of non-pregnant, dregnant and puerperal myometrium. The administrated sexual hormones were various estrogens and progestins. Oxytocin, Methylergometrine tartrate and Acetylcholine chloride were used for inducing the contraction of rat uterus. ChE activities of serum and placenta were simultaneously measured. The obtained results were as follows : 1) ChE activities in myometrium decreased in estrus and after castration, and increased in diestrus. However, ChE activities in serum were high in estrus and low in diestrus. 2) ChE activity in myometrium showed a rapid decrease up to the 14th day of pregnancy, and very slowly decreased from the 14 day through labor. Then, ChE activity was recovered to the value in non-gravid period 3 to 6 days after delivery. ChE activity in antiplacental site of myometrium was higher than in placental site. ChE activity in placenta was higher in late pregnancy than in mid pregnancy. ChE activity in serum increased during pregnancy but its deviation range was rather large. Then, this activity in serum gradually decreased during puerperium and became lower on the 6th day post partum than in non-gravid period. 3) Effects of estrogens and progestins on ChE activities in pregnant myometrium were nct remarkable. ChE activities in placenta and serum were also unchanged by estrogens and progestins. 4) ChE activities in puerperal myometrium were diminished by the administration of estradiol benzoate (1 mg or 100μg), estrone (1 mg or 100μg) or estriol (1 mg) for 6 days, but not changed by the administration of 10μg of these estrogens or 100μg of estriol. On the other hand, ChE activities of puerperal myometrium were slightly diminished by the administration of progestins (1 mg). ChE activities of serum in puerperium became high, as in pregnancy, after the administration of 1 mg of estrogens for 6 days. 5) ChE activity was slightly low after the administration of oxytocin, but no effect of it was found in vitro. Methylergometrine tartrate and acetylcholine chloride had no remarkable effects on ChE activities in myometrium. ChE activities in serum and placenta were almost unchanged after administration of oxytocin, methylergometrine tartrate and acetylcholine chloride. 6) ChE activities were low in myometrium and placenta of uterine horn with dead fetus.