Postnatal development, sexual difference and sexual cyclic variation of prolactin cells in rats: special reference to...

During the postnatal development of rat pituitary it has been shown that PRL cells appear oval, polygonal or cup shaped in both sexes. The oval cells first appear on Day 10 after birth. Development of the latter two shapes is delayed to Days 20 and 30, respectively. The polygonal shaped cells become predominant with sexual maturation. Some of them surround the gonadotrophs with their elongate, cytoplasmic processes, taking on the appearance of cup cells. Although the PRL cells are more numerous in the female than in the male, the cup shaped cells are inverse. Further it is noted that the immunostainability of the oval and polygonal cells varies during the estrous cycle; the weakest reaction was revealed at estrus and the strongest at dioestrus. Those immunohistochemical findings may suggest that the oval cells are premature, the polygonal ones mature and the cup ones particularly differentiated. The topographic affinity between the cup cells and the gonadotrophs may be a morphological indication of their intimate functional relationship.