Document Detail

Estradiol increases the Bax/Bcl-2 ratio and induces apoptosis in the anterior pituitary gland.
MedLine Citation:
PMID:  19684383     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Estrogens are recognized as acting as modulators of pituitary cell renewal, sensitizing cells to mitogenic and apoptotic signals, thus participating in anterior pituitary homeostasis during the estrous cycle. The balance of pro- and antiapoptotic proteins of the Bcl-2 family is known to regulate cell survival and apoptosis. AIMS: In order to understand the mechanisms underlying apoptosis during the estrous cycle, we evaluated the expression of the proapoptotic protein Bax and the antiapoptotic proteins Bcl-2 and Bcl-xL in the anterior pituitary gland in cycling female rats as well as the influence of estradiol on the expression of these proteins in anterior pituitary cells of ovariectomized rats. METHODS/RESULTS: As determined by Western blot, the expression of Bax was higher in anterior pituitary glands from rats at proestrus than at diestrus I, Bcl-2 protein levels showed no difference and Bcl-xL expression was lower, thus increasing the Bax/Bcl-2 ratio at proestrus. Assessed by annexin V binding and flow cytometry, the percentage of apoptotic anterior pituitary cells was higher in rats at proestrus than at diestrus I. Chronic estrogen treatment in ovariectomized rats enhanced the Bax/Bcl-2 ratio and induced apoptosis. Moreover, incubation of cultured anterior pituitary cells from ovariectomized rats with 17beta-estradiol for 24 h increased the Bax/Bcl-2 ratio, decreased Bcl-xL expression and induced apoptosis. CONCLUSION: Our results demonstrate that estradiol increases the ratio between proapoptotic and antiapoptotic proteins of the Bcl-2 family. This effect could participate in the sensitizing action of estrogens to proapoptotic stimuli and therefore be involved in the high apoptotic rate observed at proestrus in the anterior pituitary gland.
Ver??nica Zaldivar; Mar??a Laura Magri; Sandra Z??rate; Gabriela Jaita; Guadalupe Eijo; Daniela Radl; Jimena Ferraris; Daniel Pisera; Adriana Seilicovich
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-08-14
Journal Detail:
Title:  Neuroendocrinology     Volume:  90     ISSN:  1423-0194     ISO Abbreviation:  Neuroendocrinology     Publication Date:  2009  
Date Detail:
Created Date:  2009-10-15     Completed Date:  2010-01-11     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0035665     Medline TA:  Neuroendocrinology     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  292-300     Citation Subset:  IM    
Instituto de Investigaciones en Reproducci??n, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
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MeSH Terms
Annexin A5 / metabolism
Apoptosis / physiology*
Blotting, Western
Cell Count
Diestrus / physiology
Estradiol / metabolism*
Estrogens / metabolism
Estrous Cycle / physiology*
Flow Cytometry
Pituitary Gland, Anterior / physiology*
Proestrus / physiology
Proto-Oncogene Proteins c-bcl-2 / metabolism*
Rats, Wistar
Time Factors
bcl-2-Associated X Protein / metabolism*
Reg. No./Substance:
0/Annexin A5; 0/Bax protein, rat; 0/Estrogens; 0/Proto-Oncogene Proteins c-bcl-2; 0/bcl-2-Associated X Protein; 50-28-2/Estradiol

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