RESUMO
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 degrees C 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.