Hormonal control of gap junctions in the myometrium.

Myometrial tissues from immature, ovariectomized mature, and pregnant rats were examined by thin-section or freeze-fracture electron microscopy for the presence of gap junctions following treatment with steroid hormones and inhibitors of prostaglandin synthesis. Gap junctions were present in the myometrium of immature rats after repeated injections of estradiol or diethylstilbestrol (500 micrograms/day). The frequency of gap junctions in immature rats after estradiol treatment was similar to that found during delivery. Concomitant administration of indomethacin or meclofenamate with estradiol (50 and 500 micrograms/day) for 3 or 4 days enhanced the effect of estradiol on gap junctions. Progesterone depressed the response of 500 micrograms/day estradiol and both 50 and 500 micrograms/day doses of estradiol when administered together with the inhibitors of prostaglandin synthesis. Gap junctions were also present in the myometria of ovariectomized mature rats after treatment with estradiol by itself or together with indomethacin, and these effects were suppressed by concomitant progesterone administration. These results indicate that the steroid hormones and prostaglandins may interact to modulate the presence of gap junctions in the myometrium.