The influence of oestradiol benzoate and progesterone on the secretory activity of the epithelium of the ampulla tubae in ovariectomized ewes: an electron microscopical study.
The influence of oestradiol benzoate (ODB) and progesterone on the ultrastructural organization of secretory and ciliated cells of the ovine oviduct was studied in ovariectomized animals. In untreated control animals, the absence of any influence of ovarian steroids resulted in a low cuboidal epithelium with a quiescent ultrastructural appearance. A loss of cilia has not been clearly established. The first sign of an oestrogenic influence, such as an increasing number of ribosomes and RER profiles can be observed 24 hours after a single injection of 75 mcg ODB, but immature granules do not appear in the cells until the third day after treatment. In normal cycling ewes, however, immature granules and release can be observed on D-O (first day of heat) and on D-1, i.e., 1-2 days after the peak level of oestradiol-17 beta. Some possible explanations for this difference in time are discussed. On the fourth and fifth day after ODB treatment, a similar ultrastructural organization of the secretory cells has developed as on D-2 and D-3 of the oestrous cycle. A combined treatment of ODB and progesterone resulted in a distinctly lesser secretory activity than with ODB only. An extended ODB treatment, consisting of three daily injections of 8.25 mcg ODB during 5-9 successive days, did not prevent release, The probability that a declining  oestrogen level serves as the trigger for the onset thereof, must be excluded. It is concluded, that progesterone is probably not involved in creating the optimal environment in the ampullae tubae, which seems to be essential to a satisfactory completion of processes like survival of the gametes, fertilization and early embryonic development. Progesterone might be able to shorten the response of the epithelium to oestrogen, so that the optimal intratubal environmental conditions are attained at the proper time after ovulation.
D000818:Animals; D002923:Cilia / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D004848:Epithelium / Q000648:ultrastructure; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004971:Estrus; D005187:Fallopian Tubes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D005260:Female; D008928:Mitochondria / Q000648:ultrastructure; D010053:Ovary / Q000187:drug effects*; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology*; D012270:Ribosomes / Q000648:ultrastructure; D012756:Sheep; D013997:Time Factors
D011374:Progesterone; D004958:Estradiol