Abstract: 217

IMMUNLOCALIZATION OF TISSUE INHIBITOR OF METALLOPROTEINASES 1, 2, AND 3 DURING PROSTAGLANDIN F₂-INDUCED LUTEOLYSIS.

William A. Ricke^{1 *}, Freddie N. Kojima^{1 *}, Michael F. Smith^{1 *}
Department of Animal Sciences, University of Missouri-Columbia, Columbia, MO ¹

Luteolysis is characterized by extracellular matrix (ECM) remodeling including loss of cell adhesion to ECM, apoptosis, and a decrease in progesterone. Matrix metalloproteinases (MMPs) are a family of enzymes that collectively degrade each of the proteinaceous components of the ECM and are specifically inhibited by tissue inhibitor of metalloproteinases (TIMPs). Large luteal cells (LLCs) may have an important role in regulating luteal ECM remodeling since LLCs are the primary source of MMPs, TIMPs and prostaglandin F₂ (PG) receptors. We have previously described a decrease in luteal TIMP 1 by RIA and immunohisotchemistry as early as 6 h post PG injection. The objective of this study was to further characterize the histochemical depletion of TIMP 1 within LLCs and to determine if PG affects the localization of other TIMPs. Ovine corpora lutea (CL) were collected (n=5/group) at 0, 0.5, 1, 2, and 4 h after injection of PG on day 10 of the estrous cycle. To reduce the effects of incubation times on variation of intensity of staining, individual animals representing all treatment groups were placed on an individual slide. As expected, TIMP 1 was primarily localized throughout the cytoplasm of LLCs ( > 22 µm diameter; round nucleus) in 0 h CL. However, by 0.5 h post PG administration, cytoplasmic staining within LLCs was markedly decreased and specific punctate staining appeared; this reduced cytoplasmic staining was maintained through 4h. Alternatively, staining for TIMPs 2 and 3 appeared unchanged by PG. The preceding observations suggest that an early affect of PG on luteal tissue is to specifically reduce TIMP 1 within the LLC. The apparent decrease in TIMP 1 may increase the MMP:TIMP 1 ratio and thereby facilitate the process of luteolysis.

    This abstract is being presented on Monday, August 2 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.