REGULATION OF UROKINASE-TYPE AND TISSUE-TYPE PLASMINOGEN-ACTIVATOR BYRELAXIN IN THE UTERUS AND CERVIX OF THE PREPUBERTAL GILT

Changes in plasminogen activator are associated with the reproductive tissue remodelling that occurs during growth. Given the trophic effect s of relaxin on the pig uterus and cervix, the present study was desig ned to examine the impact of relaxin on urokinase and tissue-type plas minogen activator (uPA and tPA) protein and activity in the uterus and cervix of prepubertal pigs. After relaxin administration in vivo to i nduce growth of the immature uterus and cervix, plasminogen activator activity was measured in uterine flushes and uterine and cervical tiss ue using a chromogenic substrate assay. Immunoreactive uPA and tPA pro tein in uterine flushes and uterine and cervical tissue was detected b y western blotting. Urokinase plasminogen activator activity was signi ficantly higher (P < 0.05) in uterine flushes from relaxin-treated ani mals than in controls. However, there was no change in uterine flush t PA activity or protein in response to in vivo relaxin treatment. There was no evidence for acid-labile inhibitors of plasminogen activator i n uterine flushes of any of the animals. Cell-associated uterine tissu e uPA and tPA activity, as well as protein, were similar in relaxin-tr eated and control prepubertal pigs. In the cervix, cell-associated tPA activity decreased significantly (P < 0.05) in relaxin-treated animal s, while cervical uPA activity was unchanged. These results support th e view that at least one means by which relaxin promotes pig uterine g rowth is by increasing uterine secretion of uPA. In addition, these st udies suggest that relaxin administration in vivo to prepubertal gilts has tissue-specific effects with respect to plasminogen activator.