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The effects of 100 mg/kg mifepristone administration from 1 to 5 postnatal days on formation of the female reproduction functions were studied. It has been shown that neonatal blockade of progesterone receptors resulted in significant decline of morphometric parameters of the adult rat uterus, as well as disturbance sex steroids secretion and decrease density of uterus progesterone receptors in the oestrus. Neonatal administration of mifepristone did not change the rat ability to reproduction in favorable condition, but induced significant fetus resorption under the gestation pathology. These data suggest that violation of progesterone receptors mechanisms in neonatal period of life exert negative influence on the female reproduction functions in adult. We suggest, that neonatal treatment of mifepristone can been used as a model of progesterone receptors deficit in the adult rat uterus.

The aim of this study was to evaluate the effects of single injection of 0.5 mg progesterone in neonatal stage of development on morphometric parameters of the adult rat uterus. The results showed that there were no changes ofendometrial morphometry in respect to oestrous cycle in neonatal treated rats. Neonatal administration of progesterone decreased the myometrium thickness in oestrus and dioestrums owing to circular muscle layer, and disturbed sex steroids secretion during the oestrous cycle. These data suggest that neonatal administration progesterone reduces the endometrium sensitivity to sex steroids and produces the myometrium atrophy.

Structure of the blood bed has been studied in normal rat uterus and at ageing. Phenomena of involutive changes in the blood bed have been demonstrated. They depend on the process of sclerosis in the organ and desolation of vessels.

Age peculiarities of common structure of the microcirculatory pathways, specific volumes and amount of microvessels, zonal parameters of pericapillary microcirculation of metabolites, glycosamine glycans and glycoproteins contents, phosphatase and ATPase activity, collagen and elastic fibers of the microcirculatory bed vessels have been studied in 190 unchanged uteri, beginning from 36-week-old fetuses up to 35 years of age. The microcirculatory bed of myometrium during the period of postnatal ontogenesis investigated possesses a polymer-homonomous structural organization; its base make myoangiomas, including the terminal arteriole with precapillaries and collecting venule, that run from it. Similar structure of the myometrium microcirculatory pathways is already observed in fetuses of late antenatal period. In endometrium formed glanduloangionomas are revealed in the prepubertal age. Increase in glycosamine glycans contents is stated in the microvessel walls and in the uterine stroma during the process of its development. Compensatory-adaptive changes in the uterine microcirculatory bed are described during the newborn period up to the puberty. Functionally mature structures of the microcirculatory pathways in the submucosal and vascular layers of myometrium, endometrium and in the cervix uteri are found to be formed earlier than in other areas of the organ.

Study of the effects of octestrol, 17-hydroxyprogesterone caproate and tamoxifen on uterine cell proliferation in golden hamsters aged one to twenty days has shown the existence in the uterine epithelium of two cell populations with varying sensitivity to sex hormones. The cells of uterine glands being formed by day 12 of postnatal ontogenesis were found to be insensitive to the proliferation-inhibiting effect of progesterone and little sensitive to the proliferation-stimulating action of the estrogen. The epithelial cells lining the uterine cavity show a high sensitivity to sex hormones. The absence of changes in proliferative activity of the epithelial cells exposed to tamoxifen allows a suggestion that ontogenetic changes in the proliferative activity of the uterine cells do not depend on the presence of endogenous hormones.