UTERINE ENDOCRINOLOGY AND PARACRINOLOGY - INSULIN-LIKE GROWTH-FACTOR BINDING PROTEIN-1 AND PLACENTAL PROTEIN-14 REVISITED

A large number of proteins and peptides have been identified in the en dometrium where they are likely to exert local biological effects. The se substances may be enzymes, their inhibitors, proteinases, proteinas e inhibitors, hormones, or bioactive peptides with diverse functions. Endometrial function and embryo-endometrial interactions require synch ronized actions between endocrine and local factors. As examples of lo cal factors recent studies on the insulin-like growth factor (IGF) sys tem and placental protein 14 (PP14) are reviewed. IGF binding protein- 1 (IGFBP-1) and PP14 are products of the secretory phase endometrium: IGFBP-1 is produced by decidualized stromal cells and PP14 by glandula r epithelial cells. IGFBP-1 may inhibit the action of IGFs at the endo metrial-trophoblastic interphase, and it may also have a role in strom al-epithelial interaction. PP14 has immunosuppressive properties, and recent findings indicate that it may play a part in the fertilization process by inhibiting binding of spermatozoa to the zona.