[Changes in lactotropocytes following administration of a pineal factor which stimulates prolactin secretion]

Effects of a factor extracted from the epiphysis on the ultrastructure of adenohypophyseal cells of immature female rats have been stuided. This factor exerted it effects mainly on lactotropocytes on stimulating their differentiation and proliferation. In the lactotropocyte cytoplasm, ultrastructural changes were noticed in elements of the protein-synthesizing system suggesting a sharp enhancing of the synthesis and release of prolactin. The study supported the earlier supposion that the epiphyse may contain a factor similar in its effect to hypothalamic prolactoliberin.