Alterations in gap junctions of human endometrial epithelial cells during normal menstrual cycle--freeze-fracture...

Gap junctions between human endometrial epithelial cells were studied at various phases of the normal menstrual cycle by freeze-fracture electron microscopy. The junctions changed in number and size according to the phases of the menstrual cycle. Only small and few gap junctions were found in the early proliferative phase. In the early secretory phase the junctions were larger and found more often in the earlier phase. In the late secretory phase the junctions were much smaller than in the early secretory phase. The cyclical changes of the junctions may have a role in controlling the proliferation and differentiation of the endometrial epithelium.