FINE STRUCTURAL CHANGES OF UTERINE SMOOTH MUSCLE CELL BOUNDARY DURING GESTATION

Biopsies from virgin nulliparous and term pregnant guinea pig uteri were prepared for electron microscopy. Smooth muscle cells of the myometrium became larger and more irregular in outline due to the increase in the number of outpouchings and irregular processes of the cell border. The intercellular space became wider due to an increase in the amount of ground substance and collagenous fibers. A thick, fairly uniform basement membrane invested the cell and a basement membrane-like material was seen in the intercellular compartment. Pinocytotic vesicles became numerous and were arranged in rows along the subsarcolemmic area, or in groups of large numbers in the cellular processes. These observations and their possible role in the increased metabolism of the uterine smooth muscle cell during pregnancy were discussed. © 1969.