MORPHOLOGICAL-CHANGES IN THE SMOOTH-MUSCLE CELLS OF THE MOUSE LOWER OVIDUCT DURING PREGNANCY AND POSTPARTUM

The muscle coat of the lower region of the mouse oviduct undergoes mor phological changes during pregnancy and post-partum. Ultrastructural e xamination and morphometrical findings show that, during pregnancy, th e smooth muscle cells undergo a significant increase in both the numbe r of mitochondria and caveolae and in the extension of the rough endop lasmic reticulum and Golgi apparatus, suggesting an enhancement of met abolic activities, especially protein synthesis. Within two days after delivery, the number of mitochondria and caveolae is similar to that of non-pregnant mice, whereas the extension of the rough endoplasmic r eticulum and Golgi apparatus further increases significantly. The cyto logical signs of enhanced protein synthesis in the smooth muscle cells of the lower oviduct during pregnancy and, especially, in the post-pa rtum period are probably related to a remodelling of the intercellular connective tissue matrix.