Histodifferentiation and cytodifferentiation in rabbit endometrium. A comparison of the effects of progesterone and various progesterone metabolites

The effects of progesterone, 20α-hydroxy-pregn-4-en-3-one, (20α-OH-P) 17 α hydroxyprogesterone (17α-OH-P) and 5α-pregnan-3, 20-dione (5α-P) on endometrium of ovariectomized rabbits have been examined. Progesterone, at 5 mg/kg/day and at 1.7 mg/kg/day increased the number of mitotic figures observed in luminal and glandular epithelium after 5 days of treatment and induced considerable arborization. None of the other compounds induced significant arborization and only 10 mg/kg/day of 20α-OH-P increased the mitotic index in luminal and glandular epithelium. Administrations of 20α-OH-P, 17α-OH-P or 5α-P resulted in the appearance of very large, pale cells in the luminal epithelium which were not present in progesterone treated rabbits. Cytochemical techniques revealed no specific staining in these cells for polysaccharides (PAS, Alcian blue), lipid (Oil Red O) or for blastokinin, a progesterone-inducible, uterine protein, examined by the fluoroscein isothiocyanate labeled antibody technique. The possibility of an apparent dissociation between histodifferentiation and cytodifferentiation is discussed.