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Abstract:
The effect of aging upon ability of the uterus to respond to a deciduagenic stimulus was studied by transmission electron microscopy. Particularly, subtle structural characteristics of decidualization were sought in stromal cells of uteri of aged rats. To negate effects of ovarian aging, rats, 4, 10 and 20-24 months of age were subjected to bilateral ovariectomy and subsequent ovarian hormone injections. As deciduagenic stimulus, sesame oil was injected into the right uterus. The left served as the hormone prime control; and only antimesometrial endometrium was examined. Oil-injected uteri of 4- and 10-month-old rats developed deciduomata which histologically were similar to published descriptions. No decidual changes were observed in the aged oil-injected uterus. Therefore, the experimental and control uteri appeared similar. Luminal epithelial cells of aged rats differed from those of younger animals primarily in possessing more lysosomes and fewer surface microvilli. Stromal cells of aged rats differed more in shape and in quantity of cytoplasm, and in these cells lipofuscin deposits were identified more frequently. Moreover, leukocytes, plasma cells and macrophages were more numerous in the aged uteri. Failure of the aged uterus to decidualize could not be correlated with any morphologic changes. Results are correlated with previously proposed explanations for failure of aged uteri to decidualize and, accordingly, to maintain implanting embryos.