INCREASED INTESTINAL MUSCLE CONTRACTILITY AND WORM EXPULSION IN NEMATODE-INFECTED MICE

Intestinal nematode infections are accompanied by mucosal inflammation and an increase in propulsive motor activity that may contribute to p arasite eviction from the gut. To examine whether differences in worm expulsion correspond to the increased intestinal muscle contractility that accompanies nematode infection, we studied mice with genetically determined differences in their ability to expel the nematode parasite Trichinella spiralis. Specifically, we examined isometric contraction of longitudinal muscle, worm counts, and inflammation, as measured by myeloperoxidase activity, in two strains of mice infected with T. spi ralis. The strong responder strain, NIH Swiss, expelled the parasites by day 16 postinfection, whereas the poorer responding B10.BR strain w as still heavily infected by day 21 postinfection. However, both strai ns developed similar increases in jejunal myeloperoxidase activity. Bo th strains demonstrated increased isometric tension development after infection, but peak tension occurred earlier in NIH Swiss mice (day 8 vs. day 12 postinfection) and was of significantly greater magnitude t han in B10.BR mice. We conclude that the ability to expel iri spiralis from the small bowel is not related to the degree of granulocyte-depe ndent mucosal inflammation but is reflected in the magnitude of the ac companying increase in force generation by intestinal smooth muscle.