[Ultrastructural localization of prolactin in the cytoplasmic processes of the cumulus granulosa cells and the microvilli of the oocyte in the rat ovary].

The cytoplasmic processes of the cumulus granulosa cells are known to play an important role in connecting these cells with the oocyte, and in supplying nutrition and some to the oocyte for its growth and maturation. And it is also found that the follicular fluid contains prolactin, and that prolactin is present in the cytoplasm of the cumulus granulosa cells and the oocyte when studied by the light microscopic histochemical staining procedure. In this study, we used the protein A-colloidal gold method for transmission electron microscopic observation of the localization of prolactin in the cumulus granulosa cells and the oocyte in the rat ovary. We proved that prolactin is present in the cytoplasmic processes of the cumulus granulosa cells and in the microvilli of the oocyte. Therefore, it is suggested that prolactin is transported from the follicular fluid through the cytoplasmic processes of the cumulus granulosa cells, and that prolactin is absorbed into the oocyte from its microvilli.