Postpartum uterine involution in sheep: histoarchitecture and changes in endometrial gene expression. Reproduction 125

After parturition, the uterus undergoes marked remod-elling during involution; however, little is known of the hor-monal, cellular and molecular mechanisms that regulate this process. The working hypothesis used in this study is that return of the ovine uterus to a non-pregnant state involves termination of a hormonal servomechanism that regulates endometrial gland morphogenesis and function during pregnancy. Suffolk ewes were ovariohysterec-tomized on postpartum days 1, 7, 14 or 28. Serum concen-trations of oestradiol were high at parturition, declined to postpartum day 4, peaked on postpartum day 6, and then declined and remained low thereafter. Progesterone was undetectable in plasma from ewes post partum. Uterine wet mass and horn length decreased after postpartum day 1, but ovarian mass did not change. Residual placenta