Abstract
Summary
We have compared the estrous cycles, decidual cell response and the quantities and biochemical characteristics of the estrogen and progesterone receptors in the uterus of aged (>20 months) and young (<10 month), virgin rats. Whereas the young animals showed estrous cycles of normal duration, the aged rats were either pseudopregnant or in anestrus. Old rats failed to show a decidual cell response. Uteri from ovariectomized estrogen primed rats weighed significantly more in the aged compared to the young rats. In the old rat, the absolute amount of estrogen receptor was less than half the amount found in the young animals. The progesterone receptor levels were similar in both age groups. Administration of progesterone failed to decrease estrogen receptor levels in the old rats. The young animals had a greater proportion of progesterone receptor population sedimenting at higher S values than the receptors from aging animals. Similarly, the uterine estrogen receptor of the aged rat sedimented at approximately 4.5S, whereas the young rats snowed estrogen receptors sedimenting at both 7.5S and 4.5S. These studies indicate that reproductive failure in the aging rat, as demonstrated by a lack of decidual cell response, is accompanied by changes in the receptors for progesterone and estrogen.
Get full access to this article
View all access options for this article.