[Killing effect of exogenous NO on cercariae of Schistosoma japonicum in vitro].

Objective: To explore the killing effects of exogenous NO on the cercariae of Schistosoma japonicum in vitro and the blocking effects of NO inhibitors.

Methods: The cercariae of S. japonicum were collected from naturally infected snails, and then formulated into a 1000 cercariae/ml suspension with RPMI 1640 medium. The relationship between the killing effects and doses of exogenous NO on cercariae were investigated through the suspension with different concentrations of NO generating agents (SNP) and negative control (without SNP). On the other hand, the blocking effects were also investigated through the suspensions being added 2.00 mmol/L SNP and four different NO inhibitors, Hb, FeSO4, L-cyst, L-arg and their combination. Additionally, the appropriate positive(2.00 mmol/L SNP) and negative controls (without NO generating agent) were used.

Results: The mortality rates of cercariae were (8.3 +/- 1.1)%, (6.26 +/- 2.3)%, and (9.3 +/- 1.0)% in the SNP 0.06, 0.1 and 0.2 mmol/L groups, respectively, and there were no statistically significant differences between the blank control group and the above-mentioned three groups, respectively (P > 0.05). The mortality rates of cercariae were(23.5 +/- 3.9)%, (46.0 +/- 1.1)%, and (59.4 +/- 0.5)% in the SNP 0.50, 1.00 and 2 mmol/L groups, respectively, and there were statistically significant differences between the blank control group and the above-mentioned groups, respectively (P < 0.05). The mortality rates of cercariae were (30.1 +/- 1.2)%, (45.1 +/- 1.4)%, (31.1 +/- 1.3)%, (34.2 +/- 3.1)%, (47.8 +/- 2.0)%, (49.1 +/- 0.6)%, and (44.2 +/- 0.1)% in the 2.00 mmol/L SNP suspensions which were added of Hb, FeSO4, L-cyst, L-arg, FeSO4+L-cyst, FeSO4+L-arg, FeSO4+L-arg+L-cyst, respectively. Compared with the 2.00 mmol/L SNP suspension, the mortality rates of the above-mentioned groups declined, and there were statistically significant differences (P < 0.05).

Conclusion: There are killing effects of exogenous NO on the cercariae of S. japonicum in vitro, and four different NO inhibitors, Hb, FeSO4, L-cyst, L-arg and their combinations have some different degrees of blocking effects.