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Biomarker discovery in rat plasma for estrogen receptor‐α action
Author(s) -
Holt Tom G.,
Flick Rosemarie B.,
Rohde Ellen,
Griffin Patrick,
Rohrer Susan P.
Publication year - 2005
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200500405
Subject(s) - agonist , chemistry , blood proteins , partial agonist , estrogen receptor alpha , alpha (finance) , estrogen receptor , receptor , in vivo , medicine , endocrinology , prolactin , estrogen , biomarker , hormone , biology , biochemistry , microbiology and biotechnology , cancer , breast cancer , construct validity , nursing , patient satisfaction
To support in vivo screening efforts for estrogen receptor (ER) subtype selective therapeutic agents, we initiated work to discover surrogate markers (biomarkers) in blood plasma that would change in response to ER subtype‐specific action. We used a proteomic approach employing strong anion exchange chromatography (SAX), PAGE, and MS to identify potential plasma markers for selective ER‐α action. The methodology was used to compare blood from vehicle‐treated rats to blood from rats treated with either 17β‐estradiol (an ER‐α/ER‐β agonist) or compound 1 (17α‐ethynyl‐[3,2‐c]pyrazolo‐19‐nor‐4‐androstene‐17β‐ol, an ER‐α‐selective agonist). Blood samples were first fractionated by SAX to separate fractions containing dominant common plasma proteins from fractions enriched for less‐abundant plasma proteins. 1‐D PAGE analysis of fractions depleted of dominant plasma proteins revealed treatment‐specific changes in protein profiles. Protein bands that changed reproducibly in response to ER‐α action were excised from the gel, separated by capillary LC, and identified by microspray ESI‐MS. Using this method, the plasma levels of two proteins, transthyretin and apolipoprotein E, were shown to decrease in response to ER‐α agonism. The method lacked the sensitivity to identify the known, 1000‐fold less‐abundant, estrogenic marker prolactin (PRL). However, using a commercial RIA and immunoblots, we showed that PRL levels increase significantly in response to treatment with the ER‐α selective agonist, compound 1 .