Variations in the morphology and Ca2+-ATPase activity of the ovarian surface epithelium in rats.

Abstract

The ultrastructure and cytochemical localization of Ca2+-activated adenosine triphosphatase (Ca2+-ATPase) activity of the ovarian surface epithelium in immature rats and in adult rats during the estrous cycle and pregnancy were investigated at both light and electron microscopical levels. In the adult rat ovaries at all stages of the estrous cycle, the intensity of Ca2+-ATPase activity and ultrastructure of the surface epithelium were considerably varied in the different regions on the same ovary. The variations in the morphology and Ca2+-ATPase activity likely provide evidence for the differences in the functional activity of the surface epithelium, which are related to the topographical connection with adjacent structures of ovarian cortex, i.e., corpus luteum, preovulatory Graafian follicles, interstitium containing small follicles. In the adult rat ovaries at all reproductive stages, the cuboidal or columnar surface epithelial cells were found on the interstitium containing small follicles. In some places, the columnar surface epithelial cells, forming crypts of the epithelium, invaginated into the ovarian proper. This type of surface epithelial cell had well-developed microvilli on its apical membrane, and showed intense Ca2+-ATPase activity on its apical and lateral membranes. The squamous surface epithelial cells were found on the surface of corpus luteum and preovulatory Graafian follicles. These cells had a low number of microvilli and less activity of Ca2+-ATPase on the apical membrane. In the immature rat ovaries, the surface epithelial cells were in part squamous, in part cuboidal. Both types of surface epithelial cells had few microvilli. Ca2+-ATPase activity on the apical membrane was considerably less on all surfaces of the ovaries. It seems that the transport function of the surface epithelium in the immature ovary is not active as compared with the mature ovary.These results suggest that the surface epithelium may have an active function of local absorption and/or transepithelial transport between pelvic cavity and ovarian proper, and its functional activity is associated with the reproductive function of the ovary.