The difference in sex hormone dependence for gap junction formation in the muscles of uterine leiomyoma and normal myometrium.

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.