HORMONAL-CONTROL OF APOPTOSIS IN HAMSTER UTERINE LUMINAL EPITHELIUM

The hamster uterine luminal epithelium undergoes cyclic morphological changes, which include mitosis and hypertrophy prior to ovulation and degenerative changes after ovulation. We have previously shown that the degenerative changes are symptoms of estradiol (E2) withdrawal; they occur within 24 hours after ovariectomy, can be prevented by E2 treatment, and are associated with a decline in the content of uterine nuclear E2 receptor (West et al., 1978). In this report, the results of an electron microscopic study of the uterine luminal epithelium in cycling and hormonally altered hamsters are described. During estrus and after ovariectomy, the death of numerous epithelial cells occurs by apoptosis. The ultrastructural alterations in such cells include condensation and margination of the chromatin, cytoplasmic condensation, amoeboid changes in cell shape with formation of pseudopodial extensions, and nuclear and cytoplasmic fragmentation. The cell fragments, or apoptotic bodies, accumulate near the basal lamina, and are then phagocytosed by macrophages, and possibly by neutrophils as well. The ultrastructural features of cell death by apoptosis in the hamster uterus are similar to those observed by others in a variety of tissues. Because of the periodic, hormonally regulated occurrence of extensive apoptosis in the hamster uterine epithelium during the estrous cycle, this system is well‐suited for further investigations on the ultrastructural alterations that occur in cells undergoing apoptosis. In addition, apoptosis appears to be a sensitive morphological endpoint of E2 withdrawal in the hamster uterine luminal epithelium. Copyright © 1979 Wiley‐Liss, Inc.