Hormonal control of pinocytosis in the uterine epithelium of the rat.

Ovariectomized rats were treated with oestradiol-17 beta and/or progesterone to mimic the hormonal parameters inducing uterine sensitivity for implantation. The degree of pinocytosis of trypan blue and ferritin in the endometrial cells was examined. Significant epithelial pinocytosis of trypan blue occurred after a 3-day treatment of progesterone, and uptake was independently increased by priming with oestrogen and by oestradiol given on the 3rd day of progesterone treatment. Progesterone treatment caused uptake of ferritin by the epithelial cells; in control animals epithelial and stromal cells were involved. Oestrogen priming enhanced ferritin absorption, while 'nidatory' oestrogen had no effect. Oestradiol given alone completely blocked pinocytosis of both intraluminally injected substances.