Structural transformations of myocytes during gestation and early postpartum involution of the uterus.

Myocytes with large homogeneous vacuoles and numerous protrusions of the cytoplasm into extracellular space (manifestations of clasmatosis) were detected in rat myometrium during normal gestation and early postpartum period. The percentage of vacuolated smooth-muscle cells and numerical density of inflammatory cells in the myometrium were evaluated. The data indicate the absence of typical inflammatory reaction in the myometrium during elimination of smooth-muscle cells in the course of postpartum involution. Clasmatosis and apoptosis are hypothesized to be the main mechanisms providing reduction of the uterine weight after delivery.