Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 9 1 2014 03 15 107 113 EN Yosef Shrifi Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Ali Farahnak Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Abolfazle Golestani Department of Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mohamad Reza Eshraghian Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Ashkan Faridi Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Mohamad Bagher Molaei Rad Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. 2015 10 14   Background: Fasciola hepatica is one of the most important helminthes parasites and triclabendazole (TCBZ) is routinely used for treatment of infected people and animals. Secreted protease enzymes by the F. hepatica plays a critical role in the inva-sion, migration, nutrition and the survival of parasite and are key targets for novel drugs and vaccines. The aim of study was to determine the protease activity of ex-cretory- secretory products (ESP) of F. hepatica in the presence of TCBZ anthel-mintic. Methods: F. hepatica helminthes were collected and cultured within RPMI 1640 [TCBZ treated (test) and untreated (control)] for 6 h at 37 °C. ESP of treated and control were collected, centrifuged and supernatants were stored at -20°C. Protein concentrations were measured according to Bradford method. Protease enzymes activities of ESP samples were estimated by using sigma's non-specific protease activity assay. ESP protein bands were detected by sodium dodecyl sulfate poly-acrylamide gel electrophoresis (SDS-PAGE). Results: Mean protein concentrations in control and treated of ESP samples were determined 196.1 ±14.52 and 376.4 ±28.20 μg/ml, respectively. Mean protease enzymes activities in control and treated were 0.37 ±0.1 and 0.089 ±0.03 U/ml, respectively. Significant difference between proteins concentrations and protease enzymes activities of two groups was observed (P<0.05). SDS-PAGE showed dif-ferent patterns of protein bands between treated and control samples. Conclusion: The TCBZ reduced secreted protease enzymes activities and possibly effects on invasion, migration, nutrition and particularly survival of the parasite in the host tissues. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/427 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/427/311