Rat myometrial smooth muscle cells show high levels of gap junctional communication under a variety of culture conditions.

Gap junctional communication was examined in rat myometrial smooth muscle cells cultured under a variety of conditions. As a functional measure of gap junctional communication, donor cells were microinjected with the fluorescent dye, Lucifer yellow, and the transfer of dye from donor cells to primary neighbor cells was monitored by fluorescence microscopy. In a myometrial smooth muscle cell line established from midgestation (Day 10) rats, high levels of dye transfer, in excess of 90%, were observed in primary cultures and at Passages 1 and 10. A slight decrease in dye transfer to 75% was observed at Passage 5. Similarly, high levels of dye transfer were observed in a smooth muscle cell line established from the myometrium of a late-gestation (Day 19) rat under subconfluent as well as confluent culture conditions. Myometrial smooth muscle cell cultures established from sexually immature 19-day-old rats also exhibited high levels of dye transfer in primary cultures and at Passage 10. Treatment of primary myometrial smooth muscle cell cultures derived from immature 19-day-old rats with 17 beta-estradiol (50 ng/ml) and 4-pregnen-3,20-dione (150 ng/ml) for 48 h in vitro had no significant effect on the high levels of dye transfer. Thus, extensive dye transfer was observed in the rat myometrial smooth muscle cells under all culture conditions examined, regardless of sexual maturity or gestational stage of the animal, in vitro hormone treatment, or cell density.