The influence of nitric oxide (NO) on the development of adults and larvae Trichinella spiralis was examined in two strains of mice: C57BL/6 and BALB/c. The influence of aminoguanidine (AG)-inhibitor of inducible nitric oxide synthase (iNOS) administered in the first days after T. spiralis infection (1-5 dpi) on the number of adult parasites, as well as the influence of AG administered at the beginning of muscle phase of the T. spiralis infection (16-29 dpi) on the number of muscle larvae, was studied. In mice that were treated with AG from the 1st to the 5th day post infection (dpi), the numbers of adult T. spiralis were counted in intestines at 6, 9, 15, and 20 dpi. In this experiment, the impact of AG expressed as diminution of adult worms at 9, 15, and 20 dpi in BALB/c mice. The opposite effect of AG was demonstrated in C57BL/6 mice at 6 and 9 dpi. In mice in which AG was applied from the 16th to the 29th dpi T. spiralis larvae were counted at 30, 35, and 41 dpi. This experiment demonstrated that treating mice with AG at the beginning of muscle phase of the infection inhibits the reduction of muscle larvae number in mice of both strains.
The role of macrophages and their products--nitric oxide (NO) and superoxide anion (O(2) (-))--were examined in BALB/c mice reinfected with Trichinella spiralis. Mice were infected twice with 400 T. spiralis larvae; the secondary infection was performed 60 days after the primary one. Adult T. spiralis in intestines were detected from 5 to 20 days postprimary infection (dpi), and postreinfection (dpri), but the intensity of worm expulsion was greater and quicker after the reinfection. The highest muscle larvae numbers were detected from 60 dpi till 90 dpi (30 dpri), and thereafter, a great reduction was noted. The high numbers of macrophages in the peritoneal cavity of infected mice were obtained at 20 dpi, but the highest numbers of these cells from 10 to 30 dpri were observed. The production of NO by macrophages in infected mice was suppressed at 5 dpi, and then, NO release increased until 60 dpi. On the contrary, the long-lasting (5-30 dpri) suppression of NO production after T. spiralis reinfection was observed. The levels of NO in plasma and urine were lower in infected mice till 20 dpi; there were no differences in plasma and urine NO level after the reinfection in comparison to control uninfected animals. The production of O(2) (-) in peritoneal macrophages was inhibited during the first 2 weeks after infection, but the reinfection caused great increase in O(2) (-) production lasting 30 days.
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