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Abstract: 404
Thomas F. Ogle1 *, Donghai Dai1
Dept. Physiology and Endocrinology, Medical College of Georgia, Augusta, GA 1
The antiprogestational-actions of mifepristone (RU486) in the decidua basalis (DB) of the rat include enhanced PKC enzymatic activity and regulation of stromal cell survival. This study investigated the role of G1 cell cycle regulatory proteins and PKC activation in the mifepristone-induced apoptotic cascade. We examined changes in expression of Cyclin D1, the G1 phase blockers, p21 and p27, and PKC proteins by Western blotting. Rats received mifepristone (2.5 mg in propylene glycol, s.c.) 3, 6, 12, or 24 h prior to sacrifice at 1400 h on day 10 of pregnancy when stromal cells are highly proliferative. Cyclin D1 was expressed at low levels throughout pregnancy and was not altered by mifepristone. Likewise, p21, a p53 dependent inhibitor of G1 progression, was detectable throughout pregnancy and not altered by the antiprogestin. In contrast, p27, a p53 independent inhibitor of G1 progression, was enhanced 2-fold during DB regression on days 14 and 17. Mifepristone enhanced p27 within 3 h (2-fold over day 10 controls) and 6-fold by 24 h. Six hours of mifepristone enhanced PKC translocation from the cytosolic to the particulate fraction of DB homogenates indicating activation. By 12 h PKC proteins increased 5-fold in both fractions (verses day 10 controls) suggesting increased protein synthesis. To determine whether these events were associated with stromal cell death, the TUNEL method was used to detect apoptotic cells in situ. Apoptosis was first detected 12 h after mifepristone (1% of cells) increasing in frequency to 9% of cells by 24 h. Thus, mifepristone-actions include blockade of G1 progression by early induction of p27 and PKC activation which culminate in stromal cell apoptosis. Supported by NIH HD29843.
This abstract is being presented on Monday, August 2 at 1:45 PM at Todd 125.