Apposition of uterine luminal epithelium during implantation in senescent golden hamsters

Closure of the uterine luminal epithelium was examined with light and electron microscopy in 3 to 5-month-old and 14 to 15-month-old golden hamsters at 3 1/2, 4, and 4 1/2 days of pregnancy. Apposition of the uterine luminal epithelium and the subsequent changes occurring during the early stages of implantation were delayed approximately 12 hrs in senescent females. However, the sequence of events and the degree to which the uterine epithelium closed and made contact with implanting blastocysts were similar in both age groups. It does not appear that closure of the uterine luminal epithelium or blastocyst attachment to the epithelium is impaired in 14 to 15-month-old hamsters but that other factors are responsible for the declining litter size.