Abstract: 【Abstract】   Objective   To investigate the lethal effect of exogenous nitric oxide on adult worms of Trichinella spiralis in vitro.  Methods  Adult worms of T. spiralis isolated from the small intestine of Trichinella-infected BALB/c mice were cultured in RPMI 1640 medium with sodium nitroprusside（SNP） in different final concentration of 0， 0.02， 0.05， 0.10， 0.20， 0.50， and 1.00 mmol/L， 1.00 mmol/L SNP+0.15 mmol/L hemoglobin （Hb）， 1.00 mmol/L SNP+0.15 mmol/L FeSO4， 1.00 mmol/L SNP+1.00 mmol/L L-cysteine （L-cyst）， 1.00 mmol/L SNP+0.15 mmol/L FeSO4 +1.00 mmol/L L-cyst， respectively， and incubated at 37 ℃ in a humidified 5% CO2 atmosphere. On the 4th day after incubation， the adult worms were stained with safranin， and observed under light microscope. The worm mortality in the groups was analyzed.  Results  Under concentration of 0.02 and 0.05 mmol/L， SNP was not cytotoxic to adult T. spiralis with an inhibition of （1.4±1.2）% and （3.2±1.0）%， respectively. The worm mortality in the groups of SNP 0.10， 0.20， 0.50， and 1.00 mmol/L was （9.9±1.8）%， （37.7±2.5）%， （50.1±3.5）%， and （80.8±1.1）%， respectively， significantly higher than that of negative control group ［（1.9±0.2）%， P<0.05］. There was a positive linear  correlation between the worm mortality and SNP concentration in the range of 0.02-1.00 mmol/L. Combination of hemoglobin， L-cyst， FeSO4 and  FeSO4+L-cyst with 1.00 mmol/L SNP led to a decrease of the mortality from （80.8±1.1）% to （56.5±3.7）%， （69.8±2.3）%， （74.8±2.4）%， （72.7±5.6）%， respectively.  Conclusion  Exogenous nitric oxide released from SNP can kill adult worms of Trichinella spiralis. However， hemoglobin and L-cysteine+FeSO4 can reverse its lethal effect on the parasites.

Key words:  , Exogenous nitric oxide；Trichinella spiralis；Adult