Serum trypsin-inhibitory activity in five species of farmed fish

The trypsin-inhibitory activity of the serum of five cultured fish species, halibut (Hippoglossus hippoglossusL.), turbot (Scophthalmus maximusL.), arctic char (Salvelinus alpinusL.), rainbow trout (Oncorhynchus mykiss, Walbaum) and brown trout (Salmo truttaL.) was investigated. Individual fish were bled and the serum trypsin-inhibitory activity analysed using an arginine-aniline dye ester as colorimetric substrate. Results for the five species indicate that levels of α2-macroglobulin-like activity decrease significantly (P<0·05) from halibut through turbot, brown trout, char and finally rainbow trout with the lowest levels. Analysis of the total trypsin binding capacity indicates a ranking with decreasing concentration of char, turbot, halibut, brown trout and rainbow trout. Significant differences occurred only in certain cases, brown and rainbow trout were significantly (P<0·05) lower than char, and rainbow trout was significantly (P<0·05) lower than turbot. The results indicate that halibut and turbot possess a higher level of α2-macroglobulin-like activity than the other species in the study, whereas char had the highest total trypsin-inhibitory level.