The prolactin cell of the white-crowned sparrow,Zonotrichia leucophrys pugetensis

Summary The anterior pituitaries from a series of female White-crowned Sparrows,Zonotrichia leucophrys pugetensis, in the periods of oviposition, incubation, and brooding under natural conditions, have been investigated by electron microscopy. The prolactin cells occur in cephalic lobe and are characterized by large (ca. 300–600 m), polymorphic electron-dense secretory granules and an extremely well developed, lamellated endoplasmic reticulum. During incubation and brooding it is only these prolactin cells that are in an activated secretory phase, as indicated by increase in number and size, extremely well developed endoplasmic reticulum, decrease in number of mature secretory granules, and by active formation of granules in the enlarged Golgi apparatus. In the late stages of brooding, and post-breeding, the prolactin cells regress with involution of the endoplasmic reticulum and Golgi apparatus, reaccumulation of granules, and the appearance of lysosomes.The gonadotropes of both the cephalic and caudal lobes undergo progressive morphologic changes through the course of the breeding period. They are numerous and active in the ovulating bird. They undergo gradual regression during the periods of incubation and brooding to become typical broody cells.This investigation was supported by Grant No. GF-33334, U.S.-Japan Cooperative Science Program of the National Science Foundation and by Grant No. GB-28080X, also from the National Science Foundation, to Professor Farner; and by Grant No. 5R040 Japan-U.S. Cooperative Science Program of Japan Association of Science Promotion, to Professor Mikami.