Estrogen dependent regulation of estrogen receptor gene expression in normal mammary gland and its relationship to estrogenic sensitivity.
In the present study, we have examined the relationship between estradiol (E2)-dependent regulation of estrogen receptor (ER) gene expression in normal mammary glands and its relationship to progesterone receptor (PgR) gene expression using tissues from E2-sensitive and -insensitive states. Estradiol caused a time-dependent decrease in ER mRNA levels in E2-sensitive mammary glands reaching a maximum at approx 6 h, at which time the levels of PgR mRNA also reached a maximum. In contrast, in E2-insensitive mammary glands, there was no E2-dependent decrease in ER mRNA at all times tested. Experiments using dissociated cells revealed that although the epithelial cells of mammary glands from both E2-sensitive and -insensitive states contained ER mRNA, in the intact E2-sensitive mammary glands, it was the nonepithelial ER that was decreasing in response to E2. Since the epithelial cells of normal mammary glands are the primary target for E2-dependent PgR synthesis, our studies suggest that a positive correlation between E2-dependent PgR gene expression and E2-dependent downregulation of ER may simply be coincidental and may not bear any true biological relationship.
Shyamala
G
G
Lady Davis Institute for Medical Research, Montreal, Quebec.
Schneider
W
W
Guiot
M C
MC
D000818:Animals; D015536:Down-Regulation / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D007774:Lactation / Q000235:genetics / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D011980:Receptors, Progesterone / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
D012333:RNA, Messenger; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D004958:Estradiol