Reproductive Decline in Aged Female Rats

Abstract

Reproductive decline in older female rodents has been interpreted as being due to deficiencies in various segments of the reproductive tract. Previous observations, such as those of Ingramamong others, have attributed deficiencies to one or all of the reproductive organs. In the present observations of a colony of aged females, examples of deficiencies at all levels of the reproductive tract were found. There were, however, a number of these animals which did produce a normal complement of ova and which fostered their continued development.Sixty-six virgin or multiparous rats, aged 18 months or older, were caged with males and matings were noted as having taken place by the presence of spermatozoa in the vaginal smear. The females were subjected to laparotomy or were killed at intervals from 1 hr following mating until term (Table 1). An additional fifteen rats, 18 months or older, were bilaterally ovariectomized. Three weeks after spaying, these females were started on hormone replacement therapy in the form of 2 mg progesterone daily.On Days 5 and 6 of progesterone treatment, each animal received 0-5 µg oestradiol propionate. On Day 6, needle stabs (six) were made in each uterine horn. On Days 9 and 10, the animals were killed. Most of the animals were injected with either Evan's blue or pontamine blue just before being killed to facilitate the observation of any decidual reactions.In thirty-five of sixty-six animals, evidence of pregnancy was observed (Table 1 ). Ova were found in the normal stages of cleavage and in the appropriate segment of the oviducts, with the following exceptions. Five of the twenty animals examined during the tubai period had a purulent salpingitis. Corpora lutea were absent in three rats. In two females, mating occurred after 09.00 hours. Ovulation was taking place in these two animals when they were killed 1 hr after mating.Thirty-six animals were examined on Days 4 to 9 of pregnancy. The uteri obtained during Days 4 and 5 (preimplantation stages) were serially sectioned. In the six negative cases, various degrees of leucocytic infiltration were found in the mesometrial segment of the lumen. In some, the migration of lympho¬ cytes was massive. Abnormal ova were surrounded by polymorphonuclear leucocytes. When implantation had occurred in the animals killed on Days 6 to 9 of pregnancy, the average number of decidual reactions per uterine horn 121

Effect of Age upon Uterine Response to Deciduagenic Stimulus

“…Leukocytes are normally present in the endometrium of some rodents; and their numbers may vary with the stage of the reproductive cycle [ Ross and Klebanoff, 1966], An increased leukocytic accumula tion in the aged uteri in this study parallels the observations of Maibenco and Krehbiel [1973]. Increase in numbers of lymphocytes and plasma cells may indicate immunologic activity.…”

Determinants of uterine aging: lessons from rodent models

“…The epithelium will transduce the message to the underneath stroma to initiate the decidualization process [68]. As mentioned above, the uterine epithelium in old rodent has abnormal appearance during the uterine preparation to enter the receptivity, thus will fail to send the message properly and the decidualization will not form as well as in young animals [69,70]. With the progression of pregnancy in old animals, more embryos were resorbed, reinforcing that there is something wrong within the uterine decidua.…”

Characteristics of uterine aging

“…It is well established in mammals that female reproductive capacity diminishes with age; a progressive decrease in litter size has been described in rats (Asdell et al, 1941;Day et al, 1989;Ingram et al, 1958;King, 1916;Maibenco and Krehbiel, 1973;Matt et al, 1986;Miller et al, 1979), mice (Biggers et al, 1962a,b;Finn, 1962Finn, , 1963Harman and Talbert, 1970;Jones and Krohn, 1961;Sugiyama, 1961;Talbert, 19711, golden hamster (Parkening and Soderwall, 1974;Soderwall et al, 1960), and rabbit (Adams, 1970), while a progressive decline in fecundity with age has also been confirmed in women over 35 years old (Edwards et al, 1991;Stovall et al, 1991;Talbert, 1968). The reasons for this decline are not clear, and the roles of ovarian function, oocyte quality, and the endometrial environment have all been investigated.…”