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:
VILLEGAS GABUTTI CARLOS, EZQUER MARCELO, DEIS RICARDO, MALDONADO CRISTINA, SOAJE MARTA
Revista:
NEUROENDOCRINOLOGY
Editorial:
Karger
Referencias:
Lugar: Basilea; Año: 2008
ISSN:
0028-3835
Resumen:
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.