HORMONAL-REGULATION OF TISSUE INHIBITORS OF METALLOPROTEINASES DURINGFOLLICULAR DEVELOPMENT IN THE RAT OVARY

Tissue inhibitors of metalloproteinases (TIMPs) are members of a multi gene family of proteinase inhibitors that regulate the activity of met alloproteinases. To test the hypothesis that TIMPs regulate connective tissue remodeling during follicular development, rats were injected w ith PMSG (20 IU, sc), and ovaries and serum were collected at the time of pregnant mare serum gonadotropin (PMSG) administration (0 h) and a t 6, 12, 24, 36, and 48 h later for analysis of TIMP expression, metal loproteinase 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 exp ression (N = 4). For TIMP-1, PMSG stimulated a 2.4- to 2.5-fold increa se in TIMP-1 mRNA at 6 and 12 h compared to ovaries collected at the t ime of PMSG administration (i.e., 0 h control). TIMP-1 mRNA returned t o control levels within 24 h and remained unchanged through 48 h. In c ontrast to TIMP-1, TIMP-3 mRNA decreased by approx 2.5-fold at 6 h fol lowing 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 unchan ged. There was no change in metalloproteinase inhibitor activity in wh ole ovarian extracts between 0 and 36 h. However, there was an increas e in inhibitor activity at 48 h. These findings are the first demonstr ation of hormonal regulation of TIMPs during the follicular phase. The differential regulation of the TIMPs by gonadotropins, for example, a n increase in TIMP-1 and a concomitant decrease in TIMP-3 expression, may reflect different roles, sites of action, or enzyme specificity fo r the inhibitors as the follicle grows.