TROUT OVULATORY PROTEINS ARE PARTIALLY RESPONSIBLE FOR THE ANTI-PROTEOLYTIC ACTIVITY FOUND IN TROUT CELOMIC FLUID

After ovulation in salmonids, the eggs are held in the peritoneal cavi ty and bathed in coelomic fluid. Using a chromogenic peptide substrate , the anti-protease activity of brook trout coelomic fluid was measure d. Trypsin, chymotrypsin, and pancreatic elastase activities were sign ificantly inhibited by coelomic fluid containing 5.0, 10.0, and 25.0 m u g of total protein, respectively. Using subtractive cDNA cloning, we have previously characterized a set of ovarian proteins called TOPs ( trout ovulatory proteins) that are secreted into the coelomic fluid af ter ovulation. TOPs are most homologous to mammalian antileukoprotease , a heat- and acid-stable serine protease inhibitor. On the basis of t his homology, we hypothesized that the anti-trypsin activity observed in the coelomic fluid was related to the presence of TOPs. In the pres ent study, this hypothesis was supported by the acid- and heat-stabili ty of the anti-trypsin activity present in coelomic fluid. Coelomic fl uid could be heated to 50 degrees C or treated at a pH less than 5.2 w ithout a significant decrease in the inhibitory activity. Further, coe lomic fluid from which TOPs were immunoprecipitated had significantly less anti-trypsin activity than nonimmunoprecipitated controls. We pro pose that TOP proteins are uniquely produced by the ovary and secreted into the coelomic fluid to act as protease inhibitors following ovula tion.