The Effect of Maternal Age on Decidualization in the Mouse1

The response of 4- to 7-, 9-, I I-, 13-, and l5-mo.-old C57BI/6J mice to artificial decidualiiing stimuli was observed in pseudopregnant mice and in ovariectomized animals receiving injections of exogenous estrogen and progesterone. The strength of the decidual response to an injection of sesame oil into the uterine lumen declined significantly at 9 mo. of age in both pseudopregnant mice and in ovariectomized mice receiving ovarian hormone support and remained at about the same level in older mice. Intraluminal thread, as an artificial decidualizing stimulus, produced a significantly greater response than did intraluminal oil in ovariectomized, hormone-treated mice but the response declined with increasing maternal age. This study indicates that intrinsic changes occur in the uterus of aging mice which result in a decline in response to a decidualizing stimulus. Since the decline in the rate of implantation associated with increasing maternal age noted in a previous study does not parallel the decline in the decidual response observed in this investigation other factors may con-tribute to failure of implantation in old mice. r¥^HE concept that reproductive decline in •* • aging female mice is primarily due to failure of the uterus to support pregnancy wa