Effect of the Eubothrium rugosum (Cestoda) Extract on Intestinal Proteolytic Activity in Various Fish Species

Resumo

The extract of the fish tapeworm Eubothrium rugosum was found to inhibit activity of intestinal proteases in its host, the burbot. A decrease in proteolytic activity of the intestinal mucosa, when using the E. rugosum extract as an inhibitor, is comparable with that of a serine protease inhibitor PMSF. This implies that the tapeworm-produced inhibitor inactivates major intestinal serine proteases, trypsin and chymotrypsin. The tapeworm extract was also demonstrated to inhibit proteolytic activity in the intestinal mucosa of the two other fish species, zope and bream. Using the Gini index, it was found that the distribution of percent inhibition levels shows some nonuniformity across the given set of species. Namely, the tapeworm extract exerts a more selective inhibitory effect on intestinal proteases in different fish species as compared to PMSF. This indicates a partial though quite explicit species-specific selectivity of the tapeworm-produced inhibitor toward the host’s proteolytic activity which may contribute to the formation of specific host-parasite interrelationships.