Dr. Kassai Tibor - Dr. Murai Éva szerk.: Parasitologia Hungarica 10. (Budapest, 1977)
Table 5 Chymotrypsin- and trypsin-inhibitor activities measured in extracts of larval and adult stages Chymotrypsin-inhibitor Larvae 7 7 15 7 8 11 8 14 11. 5 •12. 5 Means: 10. 2 Adults 12 18 17 31 17 17. 5 Trypsin-inhibitor Larvae 13 16 6 2 7 7. 4 Adults 10 9 12. 5 11. 5 9. 5 9. 9 Discussion The present experimental results unequivocally show that plerocercoid larvas and adult stages of L. intestinalis do possess proteolytic enzyme activity. The enzyme is chymotrypsin-like, as judged from its substrate specificity, and it is dempnstrable not only in extracts of the parasite, but also in the nutrient medium in which intact specimens have been incubated. Unlike the statement of KWA (1972) and SHISHO VA-KASATOCHKINA and DUBOVSKAYA (1976), we failed to find higher activity in the homogenate of scolex and scrapings of the tegument than in the whole body homogenate. Adult specimens displayed higher proteinase activity tht n larvae (Fig. 4) in the present studies, while SHISH OVA -KASA TO CH KIN A and DUBOVSKAYA (1976) reported the reverse. It should be mentioned that these authors studied the larval and adult stages of different species, and their conclusion seems to be valid exclusively for the fish parasite Triaenophorus nodulo- sus , the larvae of which establish themselves in the liver of the host, while adult specimens in the intestine. Their findings on Schistocephalus solidus are conform to our experience with L. intestinalis , suggesting that tapeworms with similar localizations during their life ^ycle (larvae in the gut of fish, adults in the small intestine of aquatic birds) may have similar enzyme functions. At tapeworms proteolytic enzyme presumably collaborates in the extra- corporal digestion (SMYTH, 1969) which seems to take place not only at the surface of the tegument (contact digestion) (TAYLOR and THOMAS, 1968; READ, 1973), but also in the surrounding medium. Evidence that tapeworms produce protease inhibitors was obtained by assays both in parasite extracts and in maintenance media of in vitro cultivated stages. Inhibitor activity was more pronounced in the extracts than in the nutrient media, but increase of it was noted in the latter from 24 to 48 hours.