[Adaptive transformation of rat myometrium with the progression of pregnancy and after parturition].

The myometrium of various parts of uterine wall was studied in 40 albino rats--non-pregnant animals, rats at different stages of pregnancy and after parturition. The methods of immunocytochemistry (detection of apoptotic cells with the help of antibodies against the tumor necrosis factor receptor), complex morphometic and cytochemical analysis of DNA content in the nuclei and of total protein in the cytoplasm of isolated smooth-myocytes (SM). The regularities of structural reconstruction of SM population in the uterine wall at various physiological periods were detected. The realization of basic mechanisms of myometrial transformation during the pregnancy, such as hyperplasia and hypertrophy are different in various uterine parts because of their specialized functional load. At the early stages of pregnancy, small SM were found to prevail in SM populations of all the uterine part, proliferative potential was increased. By the end of gestation, the fraction of large-sized SM was increased in the horns, the synthetic processes in the cytoplasm were activated, while the fraction of medium-sized SM was increased in the corpus and the cervix. The structure of SM population in the horns on Day 7 of postpartum involution was similar to that of non-pregnant rats, in the corpus and the cervix the increase of small SM number was observed.