The secretory activity of the epithelium of the ampulla tubae in cyclic ewes: an electron microscopical study.

The ultrastructural organization of the epithelium of the ovine oviduct was studied with special reference to cyclical changes in synthesis, storage, and release of the secretory product. In contradistinction to the ciliated cells, the secretory cells have a conspicuous endoplasmic reticulum especially on the first days after onset of heat. Several types of secretion granules can be distinguished; they possibly represent different stages of maturation. The younger forms predominate during the first days of the cycle. Release of the secretory product can be observed mainly during this period, but also occur during later stages of the cycle. The peak level of oestradiol-17theta, occurring in the blood on D 16 (D 0 is the first day of heat), is presumed to be responsible for the increase in synthesizing capacity of the secretory cells during heat and first following days. The endocrine control of the release of the secretory product remains obscure: progesterone does not seem to play an essential role.