Expression and activity of ovarian tissue inhibitors of metalloproteinases during pseudopregnancy in the rat.

The present study examined the role of tissue inhibitors of metalloproteinases (TIMPs) in tissue remodeling that occurs during luteal development and regression throughout pseudopregnancy in the rat. Pseudopregnancy was induced in immature female rats by eCG/hCG priming. Animals (n = 4 per time point) were killed on Days 1, 2, 4, 8, 12, 14, and 16 of pseudopregnancy (post hCG administration), and ovaries were removed and analyzed for metalloproteinase inhibitor activity or TIMP-1, TIMP-2, and TIMP-3 mRNA expression. Inhibitory activity was highest in Day-1 samples (41.35 +/- 6.50 inhibitory units), and inhibitor activity significantly decreased (p < 0.05) thereafter to minimal values at Day 12 (8.14 +/- 2.71 inhibitory units). Methylamine hydrochloride treatment, which inactivates macroglobulin-type inhibitors, revealed that the majority of the inhibitor activity in the Day-1 samples (82.6%) and the Day-16 samples (77.3%) could be attributed to TIMPs. To further distinguish the contribution of each TIMP to this activity, Northern analysis for TIMP-1, -2, and -3 was performed. Analysis of TIMP mRNA expression revealed that TIMP-1 transcript expression was highest (p = 0.00009) at Day 1, decreased approximately 3- to 20-fold from Days 2 to 12, respectively, and again increased at Days 14-16. However, TIMP-2 expression did not change (p > 0.05) over any of the time points studied. In contrast to TIMP-1 and TIMP-2 expression, TIMP-3 mRNA expression was lowest during Days 1 and 2 of pseudopregnancy, increased approximately 4-fold at Day 4, peaked at Day 8, and remained elevated throughout the remainder of pseudopregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)