Localization of a synthetic progestin in the reproductive organs of the female baboon

The uptake and retention of a radiolabeled synthetic progestin, ORG 2058, was studied in the female reproductive system of the baboon. Four estrogen‐primed baboons were injected intravenously with 2.5 μ/kg body weight of ³H‐ORG 2058. One animal, which served as a control, received an additional injection of 2.5 mg/kg body weight of unlabeled progesterone. One hour after the injections, the animals were killed and the uterus, cervix, oviduct, vagina, and labia were removed and processed for autoradiography. The cells in the germinative layers of the stratified squamous epithelium of the cervix, vagina, and labia demonstrated nuclear localization of the label. The columnar epithelium, both surface and glandular, of the uterus and cervix sequestered the synthetic steroid; however, the nuclei of the epithelium lining the oviduct were unlabeled. The nuclei of the fibroblasts and of the smooth muscle cells were labeled in all the organs studied. These preliminary observations suggest that there is a stage in the reproductive cycle in which progesterone receptors are contained in the stromal cells of the oviduct but are absent in the epithelium.