In vitro studies on the control of human myometrial gap junctions.

In this study human myometrial tissues were examined for the presence of gap junctions by quantitative electron microscopy before and after incubation in tissue culture media with and without indomethacin. The area of gap junctions was very low in tissues from pregnant women at term but not labor, before incubation. After 24 and 48 h incubation without any treatment, segments of some of the same tissues developed many gap junctions and other tissues contained few junctions. Prostaglandin E (PGE), prostaglandin F (PGF) and prostaglandin F metabolite (PGF metabolite) levels in the media at various times were measured by radioimmunoassay. The prostaglandins increased progressively during the incubation period. Treatment of tissues with indomethacin decreased prostaglandin levels in the media and increased the numbers of gap junctions in those control tissues that developed few junctions over the same incubation interval. We conclude that the capacity of human myometrial tissues to develop gap junctions in vitro may depend upon a maturational stage in preparation for labor. Furthermore, our results suggest that products of the cyclo-oxygenase or lipoxygenase pathways may control the presence of gap junctions in the human myometrium and that changes in synthesis in these patterns may occur as part of the maturational process.