title: Intracellular dynamics in pituitary mammotropes throughout the rat estrous cycle. II. Changes in synthetic and secretory organelles.
abstract: The organellar dynamics within mammotropes (prolactin secreting cells) of the anterior pituitary were examined using morphometry throughout the four-day rat estrous cycle. Two predominant periods of maximal organellar activity were found. The first period, which occurred during proestrus, resulted in two peaks of serum PRL at 6 pm and 12 m proestrus, while the second occurred during middiestrus-2 and resulted in an increase of pituitary PRL, but not a major serum PRL peak. The mitochondrial volume rose prior to that of other organelles during early proestrus, rising 110% from 4 am late diestrus-2 to 6 pm proestrus. However, the number of mitochondria per cell remained constant throughout the cycle. The volumes of rough endoplasmic reticulum (RER) and Golgi complex reached maximal proportions at 8 pm and 12 m proestrus, respectively. The RER volume was 153% greater than at 4 am late diestrus-2, while the Golgi complex had increased by 200%. We suggest that changes in the RER and Golgi complex volumes were the result of two processes: the synthesis of new membrane and the swelling of existing complexes. This study further substantiated that the serum peak of PRL at 6 pm proestrus is the result of stored mature granules being released, whereas the PRL peak at 12 m proestrus is due to the immediate release of hormone without any storage.
mesh_terms: D000818:Animals; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D004971:Estrus; D005260:Female; D006056:Golgi Apparatus / Q000648:ultrastructure; D008928:Mitochondria / Q000648:ultrastructure; D009940:Organoids / Q000648:ultrastructure*; D010903:Pituitary Gland, Anterior / Q000648:ultrastructure*; D011247:Pregnancy; D011388:Prolactin / Q000378:metabolism*; D051381:Rats
chemical_list: D011388:Prolactin