IMBECU   20882
INSTITUTO DE MEDICINA Y BIOLOGIA EXPERIMENTAL DE CUYO
Unidad Ejecutora - UE
artículos
Título:
Pituitary Changes Involved in Prolactin Secretion Induced by Mifepristone and Naloxone during Late Pregnancy
Autor/es:
CARLOS VILLEGAS GABUTTI; MARCELO EZQUER; RICARDO DEIS; CRISTINA MALDONADO; MARTA SOAJE
Revista:
NEUROENDOCRINOLOGY
Editorial:
KARGER
Referencias:
Lugar: Basilea; Año: 2009 vol. 89 p. 200 - 209
ISSN:
0028-3835
Resumen:
Abstract BACKGROUND/AIMS: The antiprogesterone mifepristone facilitates prolactin release, an effect enhanced by administration of the opioid antagonist naloxone. The present study explores ultrastructural changes in lactotropes after mifepristone and naloxone administration, correlating them with the expression of pituitary prolactin. METHODS/RESULTS: Rats were sacrificed at 18:00 h on day 19 of pregnancy. Prolactin immunoelectron microscopy of lactotropes from control rats showed characteristics of quiescent cells with numerous small and spherical secretory granules. Naloxone administration did not modify lactotrope morphology or prolactin expression in terms of mRNA or protein abundances. Mifepristone treatment induced lactotrope activation with development of the rough endoplasmic reticulum and Golgi complex with prolactin immunoreactive small newly formed and large mature secretory granules. Mifepristone increased prolactin mRNA and protein expression. Naloxone administration to mifepristone-treated rats potentiated lactotrope activation compared with mifepristone alone showing exocytotic images of prolactin granules and some cells with evident signs of involution. CONCLUSIONS: (1) Blockade of progesterone action by mifepristone activated the lactotrope, increased significantly prolactin mRNA and protein expression and prepared the pituitary for naloxone action. (2) The high serum prolactin levels induced by mifepristone and naloxone may regulate negatively lactotrope activity as suggested by the presence of regressing cells neighboring the actively secreting cells.