Serine proteinase inhibitors of seminal plasma of teleost fish: distribution of activity, electrophoretic profiles and relation to proteinase inhibitors of blood

Anti-proteinase activity has been found in seminal plasma of eight teleost fish species: brown trout, rainbow trout, brook trout, lake whitefish, brea m, northern pike, Danube salmon and burbot. This activity correlated with s eminal plasma protein and sperm concentrations. Using a mammalian (bovine t rypsin for detecting proteinase inhibitors it was found for the first time that there are species-specific electrophoretic profiles of anti-proteinase activity. One to three bands could be identified by this method. However, additional proteinase inhibitors could be identified by using fish (cod) tr ypsin. These inhibitors were detected in seminal plasma of salmonids and co regonids and have a slow migration rate. Fast-migrating proteinase inhibito rs were present in rainbow, brown and brook trout, northern pike, whitefish and burbot. These inhibitors could be detected in brook and brown trout by using either trypsins. However, they were detected only with bovine trypsi n in rainbow trout, northern pike, whitefish and burbot. These results sugg est that multiple forms of serine proteinase inhibitors exist in seminal pl asma of teleost fish and they differ in their affinity toward serine protei nases. Seminal plasma serine proteinase inhibitors of rainbow trout migrate d during electrophoresis similarly to blood plasma proteinase inhibitors, a nd suggests that the two inhibitors may be similar or the same. Anti-protei nase specific activity was similar in blood and seminal plasma. Proteinase inhibitors of fish seminal plasma seem to be an important part of sperm phy siology, possibly related to protection of spermatozoa. Staining for detect ion of serine proteinase inhibitors also allowed detection of presence of n onspecific esterase in seminal plasma of most species. (C) 1998 The Fisheri es Society of the British Isles.