INVESTIGADORES
RAMOS Jorge Guillermo
artículos
Título:
Association of increased ERb2 expression with parity-induced alterations in the rat mammary gland
Autor/es:
KASS L; DURANDO M; RAMOS JG; VARAYOUD J; POWELL CE; LUQUE EH; MUÑOZ DE TORO M
Revista:
JOURNAL OF STEROID BIOCHEMISTRY AND MOLECULAR BIOLOGY
Referencias:
Año: 2004 vol. 91 p. 29 - 39
ISSN:
0960-0760
Resumen:
In this study, we investigated the cellular and molecular events
involved in parity-related alterations in mammary gland (MG)
proliferation and differentiation. Rat MGs were removed on day 9 of
either first (nulliparous), second (primiparous) or third (multiparous)
pregnancy. Expression of steroid hormone receptors along with cellular
biomarkers of proliferation and differentiation were quantified in all
MG tissue compartments by immunohistochemistry. Wnt-4 (a Wingless-like
morphogenic gene involved in MG development), ERbeta and ERbeta2 mRNA
were evaluated by RT-PCR analysis. Serum levels of mammotrophic
hormones were measured. In comparison to nulliparous and primiparous
rats, multiparous animals exhibited decreased luminal cell
proliferation and PR levels, whereas alpha-lactalbumin, ERalpha, ERbeta
and ERbeta2 expression were increased. In myoepithelial cells, while
parity induced a decrease in proliferative activity, subsequent
pregnancies and lactations lead to an increased state of
differentiation. Our results showed that at least two periods of
pregnancy and lactation were necessary to modify the studied
parameters. The lower proliferative activity and higher differentiation
state of the multiparous MG are associated with both a decreased PR
expression and increased ERalpha and ERbeta expression. Since ERbeta
and/or ERbeta2 isoform expression was related to parity history,
results suggest that the decreased proliferative activity and PR
expression observed in the MG of multiparous animals may be associated
with overexpression of ERbeta and/or the ERbeta2 isoform, thereby
antagonizing the proliferative effects associated with ERalpha.