Objective: To study the lethal effect of exogenous nitric oxide donor sodium nitroprusside (SNP) on the muscle larvae of Trichinella spiralis in vitro cultivation.
Methods: T. spiralis muscle larvae isolated from the infected BALB/c mice were formulated into a 1,000 larva/ml suspension with RPMI 1640 medium, and 0.1 ml suspension per orifice was cultured with SNP at 37°C in a humidified 5% CO2 atmosphere. The final concentrations of SNP were 0.02, 0.05, 0.10, 0.20, 0.50 and 1.00 mmol/L, respectively, and then the experiments were divided into 5 groups:1.00 mmol/L SNP (control group, Group A), 0.15 mmol/L FeSO4+ 1.00 mmol/L SNP (Group B), 1.00 mmol/L L-cysteine + 1.00 mmol/L SNP (Group C), 0.15 mmol/L FeSO4+ 1.00 mmol/L L-cysteine + 1.00 mmol/L SNP (Group D) and 0.15 mmol/L Hemoglobin + 1.00 mmol/L SNP (Group E). All the groups were incubated with T. spiralis muscle larvae in RPMI 1640 medium. The survivability of the muscle larvae was observed by steromicroscope and the differences of inhibition ratio among these groups were analyzed 4 d after the incubation. Results SNP 0.02 mmol/L was not cytotoxic to the muscle larvae with an inhibition of (5.50 ± 1.80) %. The mortality rates of SNP 0.05, 0.10, 0.20, 0.50, 1.00 mmol/L groups were (20.19±2.71)%, (29.21±2.12)%, (41.81±2.03)%, (47.85±3.79)%, (60.98±5.19)%, respectively, significantly higher than that of the control group[(4.93±0.25) %, all P < 0.051]. There was a positive liner correlation between the mortality of muscle larvae and SNP concentrations in the range of 0.02-1.00 mmol/L. Next, Group A, B, C, D and E led to the mortalities from (60.98±5.19)% to (49.48±1.34)%, (47.29±2.79)%, (26.28±1.37)%, (17.93±3.49)%, respectively, and all the differences between Group A and the other four groups were statistically significant (all P < 0.05).
Conclusions: Exogenous nitric oxide released from SNP can kill the muscle larvae of T. spiralis. However, hemoglobin, L-cysteine, and FeSO4 can reverse the lethal effect on the parasites. The best inhibitor was hemoglobin.