Gelatinase and proteoglycanase are metalloproteinases that govern extracellular matrix remodeling. In the present study, immature rats were primed with eCG (20 IU) and hCG (10 IU). Ovarian gelatinase and proteoglycanase activity were determined at the time of hCG administration (0 h) as well as 4, 8, and 12 h later. Gelatinase and proteoglycanase were extracted by homogenization in Triton and by heating (i.e., heat extraction). An aliquot of the heat extract was reduced and alkylated to destroy metalloproteinase inhibitors. Heat extracts not reduced and alkylated showed low levels of gelatinase and proteoglycanase activity that did not change at the different time points. However, with reduction and alkylation, gelatinolysis increased approximately 4-fold (p less than 0.05) at 4 h, 8 h, and 12 h after hCG priming. Proteoglycanase activity increased approximately 2-fold (p less than 0.05) between 0 and 8 h and declined at 12 h after hCG. The ovarian gelatinolytic activity was due to a metalloproteinase as demonstrated by the inhibition of enzyme activity by phenanthroline and EDTA (97.1 +/- 0.7% and 97.4 +/- 0.6% inhibition respectively). Proteoglycanase activity was not inhibited by phenanthroline (11.5 +/- 3.5%), suggesting that the enzyme activity was not specifically a metal-dependent enzyme. Gelatin gel zymography of the ovarian extracts demonstrated four predominant and distinct gelatin-degrading enzymes of 78, 72, 66, and 62 kDa, similar to the size of gelatinase. The present findings demonstrate a periovulatory increase in ovarian gelatinolytic and proteglycanase activity that may play a pivotal role in connective tissue remodeling associated with ovulation.

In the present study, we examined the roles of the matrix metalloproteinases collagenase, 72-kDa and 92-kDa gelatinase, and proteoglycanase in the tissue remodeling that occurs during luteal development and regression, using a pseudopregnant rat model. Pseudopregnancy was induced in immature female rats by eCG/hCG priming, and animals (n = 3 to 4 per time point) were killed on Days 1, 2, 4, 8, 12, 14, or 16 of pseudopregnancy (Day 0 = time of hCG administration). Ovaries were then removed and analyzed for either matrix metalloproteinase mRNA expression or activity. During luteal development (Day 1 of pseudopregnancy), activity of both collagenase (p = 0.009) and gelatinase (p = 0.0003), but not proteoglycanase (p > or = 0.05), was significantly greater than at all other time points. In accord with gelatinase activity, transcript levels of this enzyme were elevated at Day 1 of pseudopregnancy. Specifically, gelatinase transcript levels for the 72-kDa and 92-kDa enzymes were greatest at Day 1 (p = 0.0003 and p = 0.001, respectively), decreased 3-fold by Day 2,4-fold by Day 4, and reached 10-fold lower levels by Days 8 and 12 of pseudopregnancy. Proteoglycanase transcript could not be detected by Northern analysis during luteal development or any other time point examined in the current study. During the period of luteal maintenance (approximately Days 4-8 of pseudopregnancy in the rat), collagenase and gelatinase displayed basal levels of activity, but only proteoglycanase activity was elevated compared to luteal development levels of this enzyme. During luteal regression (Days 12-14 of pseudopregnancy in the rat), all enzymes displayed basal levels of enzyme activity. In accord with gelatinolytic activity during luteal regression, both 72-kDa and 92-kDa gelatinase mRNA were detectable at baseline levels. In contrast to the baseline levels of collagenolytic activity during luteal regression, collagenase transcript displayed peak values (approximately 8-fold greater than Day 1 levels; p = 0.004) at Day 12 of pseudopregnancy. It is concluded from these studies that collagenase and the gelatinases play a role in the tissue remodeling associated with luteal development, proteoglycanase is associated with luteal maintenance, and collagenase may contribute to the structural regression of the corpus luteum.

Tissue inhibitors of metalloproteinases (TIMPs) are membres of a multigene family of proteinase inhibitors that regulate the activity of metalloproteinases. To test the hypothesis that TIMPs regulate connective tissue remodeling during follicular development, rats were injected with PMSG (20 IU, sc), and ovaries and serum were collected at the time of pregnant mare serum gonadotropin at the time of pregnant mare serum gonadotropin (PMSG) administration (0 h) and at 6, 12, 24, 36, and 48 h later for analysis of TIMP expression, metalloproteinase inhibitor activity, and steroidogenesis. Serum estradiol levels increased from 20.9 pg/mL at 0 h to 461 pg/mL at 48 h. Northern analysis was performed for analysis of TIMP-1, TIMP-2, and TIMP-3 expression (N = 4). For TIMP-1, PMSG stimulated a 2.4- to 2.5-fold increase in TIMP-1 mRNA at 6 and 12 h compared to ovaries collected at the time of PMSG administration (i.e., 0 h control). TIMP-1 mRNA returned to control levels within 24 h and remained unchanged through 48 h. In contrast to TIMP-1, TIMP-3 mRNA decreased by approx 2.5-fold at 6 h following PMSG administration, and expression remained decreased through 48 h. For TIMP-2, the expression of the 3.5-kb transcript decreased at 24 h after PMSG, whereas expression of the 1 kb transcript was unchanged. There was no change in metalloproteinase inhibitor activity in whole ovarian extracts between 0 and 36 h. However, there was an increase in inhibitor activity at 48 h. These findings are the first demonstration of hormonal regulation of TIMPs during the follicular phase. The differential regulation of the TIMPs by gonadotropins, for example, an increase in TIMP-1 and a concomitant decrease in TIMP-3 expression, may reflect different roles, sites of action, or enzyme specificity for the inhibitors as the follicle grows.

Galanin is a 29-amino acid peptide that acts as a neuropeptide in many tissues. To date, galanin action and the hormonal regulation of galanin gene expression have not been described in the ovary of any species. To study possible ovarian expression and regulation of galanin, immature gonadotropin-primed rats were given hCG (10 IU), and their ovaries were collected 0, 4, 8, 12, and 20 h after hCG treatment for determination of galanin messenger RNA (mRNA) concentration by solution hybridization. Galanin mRNA levels progressively increased after hCG administration, peaking at 12 h (2.4-fold increase vs. 0 h), with a subsequent return to 0 h levels at 20 h. To determine a possible ovarian role for galanin, rats were killed 48 h after gonadotropin administration, their ovaries were removed, and granulosa cells were harvested. These cells and the ovarian tissue remaining after granulosa cell collection (i.e. "shells") were each cultured for 24 h with increasing concentrations of galanin (0, 10, 100, and 1000 nM) in the presence or absence of LH. The medium was examined for steroid production and metalloproteinase inhibitor activity. In granulosa cell cultures, galanin increased the levels of estradiol by 26% and had no effect on progesterone, but decreased metalloproteinase inhibitor activity by 61% in the conditioned medium. In the shell cultures, galanin increased estradiol, progesterone, and androstenedione in the medium, suggesting that galanin acts on cells other than granulosa cells or that galanin action requires a paracrine interaction between granulosa and thecal cells. Our data demonstrate that galanin message is increased by hCG, and that galanin acts to amplify ovarian steroidogenesis while decreasing metalloproteinase inhibitor activity. These findings establish that ovarian galanin mRNA is hormonally stimulated and that galanin acts as an intraovarian regulatory peptide.