A tissue inhibitor of metalloproteinases and alpha-macroglobulins in the ovulating rat ovary: possible regulators of collagen matrix breakdown

Immature female Sprague-Dawley rats were primed with 20 IU eCG at 28 days of age and treated with 10 IU hCG 48 h later. Ovulation followed at 12-14 h. Ovaries were extracted at various times after hCG by use of Triton X-100 and 10 mM CaCl2 (Triton extract) followed by heating to 60 degrees C for 6 min with 0.1 M CaCl2 in 50 mM Tris/0.15 M NaCl, pH 7.5 (heat extract). These extracts were tested for their ability to inhibit tissue metalloproteinases by use of the small uterine metalloproteinase (UMP) of the rat. The ovary contains three plasma-derived inhibitors (alpha 1-macroglobulin [alpha 1 M], alpha 2-macroglobulin [alpha 2 M], and alpha 1 inhibitor3 [alpha 1I3]) and one tissue-derived inhibitor of the tissue inhibitor of metalloproteinases (TIMP) family. alpha 1 I3 was shown to inhibit UMP and rat collagenase. The concentration of the tissue inhibitor rose 5-fold from 0.6 micrograms UMP blocked per gram wet tissue in ovaries not primed with eCG to 3.2 micrograms UMP blocked at 8 h after hCG. Over this same time interval, the sum of alpha 1M + alpha 2M per gram of ovary rose 7-fold from 3.2 to 22.4 micrograms UMP inhibited and alpha 1I3 rose 2-fold from 4.4 to 10.7 micrograms UMP inhibited. The increases in the tissue inhibitor are interpreted to be due to increased synthesis by the tissue, whereas the changes in alpha-macroglobulins are postulated to be due to increased vascularity and increased permeability of the vessels.