MORPHOMETRIC ANALYSIS OF GAP-JUNCTIONS IN NONPREGNANT AND TERM PREGNANT HUMAN MYOMETRIUM

Background and methods. Some structures in the human myometrium, namel y; caveolae, extracellular space and gap junctions were quantified in tissues from nonpregnant women, women who were not in labor, and women in spontaneous labor or oxytocin-induced labor, in order to reveal mo rphologic differences that would contribute to explaining the events l eading to labor. Transmission electron micrographs taken from tissues from twenty-four pregnant and ten nonpregnant women were studied. Resu lts. Differences were observed in cell growth which was accompanied by enlargement of the extracellular space, and in gap junctions. Gap jun ctions were demonstrated in nonpregnant women, and even in one postmen opausal woman. Their frequency and size increased gradually between gr oups of pregnant women in the order of non-labor, oxytocin-induced lab or and spontaneous labor. The increase in size of the junctions was le ss than the increase in number. Conclusions. Gap junctions are most fr equently found in human myometrial cells in spontaneous labor, which s trongly suggests a role for these structures in the termination of pre gnancy. The effect of oxytocin on the appearance of gap junctions was negligible; hence, the contribution of oxytocin to establish myometria l contractile synchronicity is thought to be minor. Caveolae are proba bly not relevant for the initiation of labor as their distribution did not differ between the groups.