IMMUNOLOCALIZATION OF TISSUE INHIBITOR OF METALLOPROTEINASES-1 WITHINOVINE PERIOVULATORY FOLLICULAR AND LUTEAL TISSUES

In previous studies, tissue inhibitor of metalloproteinases (TIMP)-1 m RNA increased in follicular tissue after the preovulatory gonadotropin surge and was expressed in luteal tissue. However, the localization o f TIMP-1 protein within ovine periovulatory follicular and luteal tiss ues is unknown. The objectives of the present study were to 1) localiz e TIMP-1 within follicles collected before and after a preovulatory go nadotropin surge and within Day 3 and Day 10 corpora lutea (CL), 2) de termine whether TIMP-1 was colocalized to Day 10 luteal cells with oxy tocin or TIMP-2, and 3) determine whether TIMP-1 was present within se cretory granules of large luteal cells. Ovaries were removed from ewes before (presurge; n = 4) or 12-14 h after (postsurge; n = 5)an LHRH-i nduced gonadotropin surge (36 h following PGF(2 alpha)-induced luteoly sis; objective 1). Additionally, ovaries containing CL were collected on Days 3 (n = 5; objective 1) and 10 (n = 4, 3, and 2 for objectives 1, 2, and 3, respectively). TIMP-1 immunoreactivity was observed withi n the granulosa cells of postsurge but not presurge follicle., On Days 3 and 10, TIMP-1 was localized within luteal tissue in a cell-specifi c manner. On Day 10, many of the cells that were immunopositive for TI MP-1 were judged to be large luteal cells on the basis of morphology ( diameter > 22 mu m; round nucleus) and colocalization with oxytocin an d TIMP-2. Electron microscopy demonstrated that TIMP-1 was localized t o secretory granules undergoing exocytosis from Day 10 large luteal ce lls. These data indicate that TIMP-1 is produced by granulosa cells fo llowing a gonadotropin surge and is packaged in secretory granules by large steroidogenic cells of the ovine CL.