Gap junction is reported to be initiated by changes in levels of
steroid hormones in the smooth muscle cells of myometrium. In order to clarify the difference in
sex hormone dependence for gap junction formation in the muscles of uterine
leiomyoma and normal myometrium, uterine
leiomyoma and myometrial gap junctions, and serum
estradiol and
progesterone levels were determined simultaneously in 23 women who had undergone simple
hysterectomy for
leiomyomas of the corpus uteri. In all tissues of the myometrium from 23 women, at least three gap junctions were found between muscle cells in the series of photographs. On the other hand, there were 7 out of 23 uterine
leiomyomas in which not even one gap junction was detected between muscle cells in the series of photographs. The phasic change in the number of gap junctions related to the menstrual cycle was detected in the muscles of uterine
leiomyoma as well as normal myometrium. Uterine
leiomyoma was characterized by less correlation between the number of gap junctions in the muscles and the concentration of serum sex
steroids, compared with those of normal myometrium. Sex
steroids may have a trophic effect on some uterine
leiomyoma, but the
sex hormone dependence of uterine
leiomyoma for gap junction formation may be less than that of normal myometrium. The present study also showed that the increased gap junction formation in myometrial muscles from women with
dysmenorrhea may be formed between myometrial cells in response to physiologic or pathologic stimuli, such as the production of local
prostaglandins, and may result in hypercontraction of the uterus.