Oestrogen and progesterone receptors in the involuting rat uterus

Abstract

Abstract. The concentrations of cytoplasmic oestrogen and progesterone receptors were measured in rat myometrium during the post partum involution of the uterus. The concentration of the oestrogen receptor declined within 24 h post partum to about 20% of the value at delivery. A slight rise in the concentration occurred during the subsequent 24 h. The concentration of the progesterone receptor remained nearly constant the first day after delivery. Thereafter it decreased just as the concentration of the oestrogen receptor had fallen one day before. The results suggest that the post partum levels of oestrogen and progesterone receptors are regulated by the same mechanisms as those known for the non-pregnant state.