Progesterone binding protein in cytosol fraction from human oviduct.

Oviducts obtained from normal women by salpingectomy were studied for progesterone binding components in cytosol by a dextran-charcoal technique and the in vitro uptake of tritiated-progesterone was also determined. All segments of the oviduct as well as the endometrium and muscle showed specific uptake after incubation for 15 minutes though only the ampullar segment had radioactiviy after incubation for 30 minutes. The specific binding components were found to be thermolabile proteins by nature and differed from the progesterone binding protein in plasma. The Kd values were estimated to be within the range of 10 (-9) to 10 (-8). The specific binding protein was identified in the mucosa and in the proximal and distal segments of oviducts obtained in the late follcular or early luteal phase of the cycle. However it was not detectable in the muscular layer.